On Mac OS X platform the QMenuBar::triggered(QAction *) fires twice

MainWindow::MainWindow(QWidget *parent) 
: QMainWindow(parent), ui(new Ui::MainWindow) 
{ 
    ui->setupUi(this); 
    connect(ui->menuBar, SIGNAL(triggered(QAction*)), this, SLOT(menuTriggerAction(QAction*))); 
} 

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

void MainWindow::menuTriggerAction(QAction * action) 
{ 
   fprintf(stdout, "Triggered action: %s\n", action->text().toStdString().c_str()); 
   fflush(stdout); 
}