Vitaly

#include <QApplication>
#include <QMessageBox>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QMainWindow mainWindow;

    auto res = QMessageBox::question(&mainWindow, QMainWindow::tr("Just in case"),
                                     QMainWindow::tr("Are you sure?"));
    if (res == QMessageBox::Yes) {
        mainWindow.show();
        return a.exec();
    } else {
        return -1;
    }
}

QSharedPointer<QDataStream> doFoo()
{
    return false;
}

QEventLoop loop;
QFutureWatcher watcher = QConcurrent::run(someFunc);
connect(&watcher, &QFutureWatcher::finished,  &loop, &QEventLoop::quit);
loop.exec();
auto result = watcher.result();