Important: Please read the Qt Code of Conduct -

Exception Triggered(read access violation) if QSerialPort instance is created with VECTOR dll(vxlapi.dll)

  • Hello,

    I have struggled with exception problem during few weeks. :(
    Please give me some tips for this~

    I'm trying to a program that receive GPS data by serial port, and send CAN message using the data.
    Development environment is,

    • IDE : Qt Creator 3.1.2(based on Qt 5.3.1)
    • Qt version : Qt5.3 MSVC2013 32bit
    • Compiler : Microsoft Visual C++ compiler 12.0(x86)
    • Device type : Desktop(Local PC)

    And for device,

    • GPS device : ASCEN GPS (GPS742)
      a. This is connected with PC by USB cable.
      b. PC recognize it by serial port(COM12, Baud115200, 8 bit, No parity, one stop bit, No flowControl).
      c. It send GPS data periodically(about 1 second.)
    • CAN device : VECTOR CAN/LIN Interface (VN1630)
      a. This is connected with PC by USB cable.
      b. It can control by dll files('vxlapi.h', 'vxlapi.dll', and 'vxlapi.lib')

    At first, I made two individual programs,

    • 'Receiving & show GPS data' : using 'QSerialPort' class. It works well.
    • 'Sending dummy CAN message' : using dll files. It works well.

    But when I merged these programs, It compiled well but generated exception error.(read access violation)

    For Debug, I made simple console project like below,

    QT += core
    QT += serialport
    QT -= gui

    TARGET = SerialPortControlExample_ref
    CONFIG += console
    CONFIG -= app_bundle

    TEMPLATE = app

    SOURCES += main.cpp


    HEADERS +=

    win32: LIBS += -L$$PWD/ -lvxlapi


    #include <QtCore/QCoreApplication>
    #include <QtCore/QDebug>
    #include <QtSerialPort/QSerialPort>
    #include <QtSerialPort/QSerialPortInfo>
    #include <windows.h>
    #include "vxlapi.h"


    int main(int argc, char *argv[])
    XLstatus xlStatus;
    QCoreApplication a(argc, argv);

    //------------ 1st Section --------------------------------------------------
    xlStatus = xlOpenDriver();
    if(xlStatus == XL_SUCCESS) qDebug() << "Open Success!!";
    else qDebug() << "Open Fail!!!";
    //------------- End of 1st Section-------------------------------------------

    //------------ 2nd Section --------------------------------------------------
    // Example use QSerialPortInfo
    foreach (const QSerialPortInfo &info, QSerialPortInfo::availablePorts()) {
    qDebug() << "Name : " << info.portName();
    qDebug() << "Description : " << info.description();
    qDebug() << "Manufacturer: " << info.manufacturer();

        // Example use QSerialPort
        QSerialPort serial;
        if (

    //------------- End of 2nd Section-------------------------------------------

    return a.exec&#40;&#41;;


    [vxlapi.h, vxlapi.lib, vxlapi.dll]

    Among above 'main.cpp' file, if one of section is commented out, it is compiled and running correctly.

    A. If 1st section is commented out...
    [Commannd Window]
    Name : "COM12"
    Description : "GPS USB Serial Interface Driver"
    Manufacturer: "Media Tek Inc."

    B. If 2nd section is commented out,
    [Commannd Window]
    Open Success!!

    But when I use both section, it is compiled well but generated exception message once I run this program, like below,
    [Exception Triggered Window]
    The inferior stopped because it triggered an exception.
    Stopped in thread 0 by: Exception at 0x77a1e066, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance).

    The debugging result is below,
    dState changed from EngineRunRequested(7) to InferiorRunOk(11) [master]
    ModLoad: 75570000 755d0000 C:\WINDOWS\SysWOW64\IMM32.DLL
    ModLoad: 76df0000 76ebc000 C:\WINDOWS\syswow64\MSCTF.dll
    (2d4.2558): Access violation - code c0000005 (first chance)

    sException at 0x77a1e066, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance) in ntdll!RtlAllocateHeap
    First chance exceptions are reported before any exception handling.
    This exception may be expected and handled.
    eax=77280334 ebx=00000000 ecx=00000010 edx=003bf1ec esi=00000000 edi=000000e0
    eip=77a1e066 esp=003bee50 ebp=003beebc iopl=0 nv up ei ng nz ac pe cy
    cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010297
    77a1e066 8b4344 mov eax,dword ptr [ebx+44h] ds:002b:00000044=????????

    *** WARNING: Unable to verify checksum for C:\JayKim\EnS\JaySW\SerialPortControlExample_ref\vxlapi.dll
    *** ERROR: Symbol file could not be found. Defaulted to export symbols for C:\JayKim\EnS\JaySW\SerialPortControlExample_ref\vxlapi.dll -
    sException at 0x77a1e066, code: 0xc0000005: read access violation at: 0x0, flags=0x0 (first chance)
    dState changed from InferiorRunOk(11) to InferiorStopOk(14) [master]
    Resolving symbol: ntdll!RtlAllocateHeap...
    <x ntdll!RtlAllocateHeap

    Obtained 0x77a1e046 for ntdll!RtlAllocateHeap (#1)
    <u 0x77a1e046 0x77a1e168

    Please let me know some tips for these issues.

    Thank you.

Log in to reply