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Type: Bug
Resolution: Done
Priority: P1: Critical
Fix Version/s: 5.11.3, 5.12.0 Beta 3
Affects Version/s: 5.9.2, 5.9.3, 5.10.0, 5.11.0
Component/s: SerialBus: MOD Bus
Labels:
None
Environment:
Ubuntu 17.04
gcc 6.3.0
Qt 5.9.2, Qt5.10.0, Qt5.11.0

Ubuntu 14.04
gcc 4.8.4
Qt 5.9.3, Qt5.10.0

Commits:
864e4a8ab514ddcd7f79106a6b447f7a1d5b5d4e (qt/qtserialbus/5.11)

Description

A timer is connected to a slot that initializes a QModbusRtuSerialMaster to send a request and wait for the reply.

First time the slot is called I receive the good response, second time I get a memory corruption.

I create a minimal project example that reproduce the error, code is attached but here is my slot:

void MainWindow::onTimerTimeout()
{
   qDebug("slot called");

   QModbusRtuSerialMaster _modbusSerialMaster;
   _modbusSerialMaster.setConnectionParameter(QModbusDevice::SerialDataBitsParameter, QSerialPort::Data8);
   _modbusSerialMaster.setConnectionParameter(QModbusDevice::SerialParityParameter, QSerialPort::NoParity);
   _modbusSerialMaster.setConnectionParameter(QModbusDevice::SerialStopBitsParameter, QSerialPort::OneStop);
   _modbusSerialMaster.setConnectionParameter(QModbusDevice::SerialBaudRateParameter, QSerialPort::Baud115200);
   _modbusSerialMaster.setConnectionParameter(QModbusDevice::SerialPortNameParameter, "/dev/ttyUSB0");
   _modbusSerialMaster.setNumberOfRetries(2);

   if(_modbusSerialMaster.connectDevice())
   {
      qDebug("connected");
      QModbusDataUnit request = QModbusDataUnit(QModbusDataUnit::HoldingRegisters, 511, 3);

      if(auto *reply = _modbusSerialMaster.sendReadRequest(request, 9))
      {
         qDebug("reply");

         while(!reply->isFinished())
         {
            QCoreApplication::processEvents(QEventLoop::AllEvents);
         }
         qDebug() << reply->result().values();

         reply->deleteLater();
      }
      _modbusSerialMaster.disconnectDevice();
   }

   timer.start();
}

and the output:

slot called
connected
reply
QVector(17920, 30676, 0)
slot called
*** Error in `/home/malacasse/dev/build-testModbus-Desktop_Qt_5_9_2_GCC_64bit-Debug/testModbus': malloc(): memory corruption (fast): 0x0000555555b1a7ff ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7908b)[0x7ffff633b08b]
/lib/x86_64-linux-gnu/libc.so.6(+0x85008)[0x7ffff6347008]
/lib/x86_64-linux-gnu/libc.so.6(__libc_malloc+0x54)[0x7ffff6348984]
/usr/lib/x86_64-linux-gnu/libstdc++.so.6(_Znwm+0x18)[0x7ffff692faf8]
/opt/Qt/5.9.2/gcc_64/lib/libQt5SerialBus.so.5(_ZN22QModbusRtuSerialMasterC1EP7QObject+0x34d)[0x7ffff7385fbd]
/home/malacasse/dev/build-testModbus-Desktop_Qt_5_9_2_GCC_64bit-Debug/testModbus(+0x3227)[0x555555557227]
/home/malacasse/dev/build-testModbus-Desktop_Qt_5_9_2_GCC_64bit-Debug/testModbus(+0x44b3)[0x5555555584b3]
/opt/Qt/5.9.2/gcc_64/lib/libQt5Core.so.5(_ZN11QMetaObject8activateEP7QObjectiiPPv+0x659)[0x7ffff6ecb869]
/opt/Qt/5.9.2/gcc_64/lib/libQt5Core.so.5(_ZN6QTimer7timeoutENS_14QPrivateSignalE+0x27)[0x7ffff6ed8057]
.......