qInstallMsgHandler() error while registering non static function

[DURGAPRASAD NEELAM]

I am designing Qt log window, So I am using qInstallMsgHandler() function to log all the debug, critical & warning messages on to QTableWidget (in below code I have not implemented It yet). I did as below

int main(int argc, char *argv[])
{
    qInstallMsgHandler(MainWindow::logMessage);
    //qInstallMsgHandler(&MainWindow::logMessage);  //I tried this also
 
    QApplication a(argc, argv);
    MainWindow w;
    qDebug()    << "info message";
    qWarning()  << "warning message";
    qCritical() << "critical message";
    w.show();
 
    return a.exec();
}

int main(int argc, char *argv[])
{
    qInstallMsgHandler(MainWindow::logMessage);
    //qInstallMsgHandler(&MainWindow::logMessage);  //I tried this also

    QApplication a(argc, argv);
    MainWindow w;
    qDebug()    << "info message";
    qWarning()  << "warning message";
    qCritical() << "critical message";
    w.show();

    return a.exec();
}

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MainWindow:

MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::logMessage(QtMsgType type, const char *msg)
{
    switch (type) 
   {
    case QtDebugMsg:
        fprintf(stderr, "Debug: %s\n", msg);
        break;
    case QtWarningMsg:
        fprintf(stderr, "Warning: %s\n", msg);
        break;
    case QtCriticalMsg:
        fprintf(stderr, "Critical: %s\n", msg);
        break;
    case QtFatalMsg:
        fprintf(stderr, "Fatal: %s\n", msg);
        abort();
    }
}

MainWindow::MainWindow(QWidget *parent) :QMainWindow(parent),ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::logMessage(QtMsgType type, const char *msg)
{
    switch (type) 
   {
    case QtDebugMsg:
        fprintf(stderr, "Debug: %s\n", msg);
        break;
    case QtWarningMsg:
        fprintf(stderr, "Warning: %s\n", msg);
        break;
    case QtCriticalMsg:
        fprintf(stderr, "Critical: %s\n", msg);
        break;
    case QtFatalMsg:
        fprintf(stderr, "Fatal: %s\n", msg);
        abort();
    }
}

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When I compile this code, I am getting below error

main.cpp:27: error: cannot convert 'void (MainWindow::*)(QtMsgType, const char*)' to 'QtMsgHandler {aka void (*)(QtMsgType, const char*)}' for argument '1' to 'void (* qInstallMsgHandler(QtMsgHandler))(QtMsgType, const char*)'
     qInstallMsgHandler(MainWindow::logMessage);

main.cpp:27: error: cannot convert 'void (MainWindow::*)(QtMsgType, const char*)' to 'QtMsgHandler {aka void (*)(QtMsgType, const char*)}' for argument '1' to 'void (* qInstallMsgHandler(QtMsgHandler))(QtMsgType, const char*)'
     qInstallMsgHandler(MainWindow::logMessage);

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Note : If I changed void MainWindow::logMessage(QtMsgType type, const char *msg); this function to static function then it is working fine.
(But if this function is static, I can not create QTableWidgetItem and add them to tableWidget so I want this function to be non static).

And one more issue i am having here, When I use static function, all the messages are printing after I close my application only.

Please let me know What is the issue.

I am using Qt4.8.6 on Windows7

Thanks In Advance.

[jefftee]

The QtMsgHandler function does not take a "this" pointer, which is why you can't use a non-static member function. Either make it a non-member function or a static member function.

Try adding a fflush(stderr) at the end of your logging function, which will ensure your messages are not buffered and shown immediately after they are written.