auto box = new QMessageBox(this);
box->setWindowTitle("Title");
box->setText("Description");
box->show();

auto box = new QMessageBox(this);
box->QWidget::setWindowTitle("Title");
box->setText("Description");
box->show();

void QMessageBox::setWindowTitle(const QString &title)
{
    // Message boxes on the mac do not have a title
#ifndef Q_OS_MAC // ->>>>> Problem here
    QDialog::setWindowTitle(title);
#else
    Q_UNUSED(title);
#endif
}