How to enable debug console?

[ChiaoHuang]

In my case, sometime I will need the console to show log for my QT process and C++ DLL library.

I found the some code and show console from Internet.

    // detach from the current console window
    // if launched from a console window, that will still run waiting for the new console (below) to close
    // it is useful to detach from Qt Creator’s <Application output> panel
    FreeConsole();

    // create a separate new console window
    AllocConsole();

    // attach the new console to this application’s process
    AttachConsole(GetCurrentProcessId());

    SetConsoleOutputCP(65001);

    // reopen the std I/O streams to redirect I/O to the new console
    freopen("CON", "w", stdout);
    freopen("CON", "w", stderr);
    freopen("CON", "r", stdin);

This is my example code

mainwindow.cpp

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

    lib.setFileName("ExampleDLL.dll");
    if(!lib.load())
    {
        qDebug() << "load ExampleDLL.dll library failed. " << lib.errorString();
    }
    else
    {
        qDebug() << "loaded ExampleDLL.dll library";
    }

    printHelloWorldFun = (printHelloWorld)lib.resolve("printHelloWorld");

}

void MainWindow::on_DebugButton_clicked()
{
    // detach from the current console window
    // if launched from a console window, that will still run waiting for the new console (below) to close
    // it is useful to detach from Qt Creator’s <Application output> panel
    FreeConsole();

    // create a separate new console window
    AllocConsole();

    // attach the new console to this application’s process
    AttachConsole(GetCurrentProcessId());

    SetConsoleOutputCP(65001);

    // reopen the std I/O streams to redirect I/O to the new console
    freopen("CON", "w", stdout);
    freopen("CON", "w", stderr);
    freopen("CON", "r", stdin);
}

void MainWindow::on_QTButton_clicked()
{
    fprintf(stdout, "Hello World from QT\n");
}

void MainWindow::on_DLLButton_clicked()
{
    printHelloWorldFun();
}

My DLL example code:

void printHelloWorld()
{
	fprintf(stdout, "Hello World from DLL\n");
}

It sometimes works and sometimes doesn't.

How to fix this issue?
Do everyone have any idea?

Thanks

[JonB]

@ChiaoHuang
Just in case opening a CON is still block-buffered, put a fflush(stdout) after your fprintf(stdout, "...\n") statements.

[ChiaoHuang]

@JonB

Thank you for your suggestion.
Unfortunately it is not working sometimes.

Thanks