Can't check the action when it has a menu?

[koilin]

QMenu *menu = new QMenu;
	QMenu *subMenu = new QMenu;
	for (int i = 0; i < 6; i++)
	{
		QAction *action = new QAction(0);
		action->setCheckable(true);
		if (i == 3)
		{
			action->setMenu(subMenu);
		}
		menu->addAction(action);
	}

QMenu *menu = new QMenu;
	QMenu *subMenu = new QMenu;
	for (int i = 0; i < 6; i++)
	{
		QAction *action = new QAction(0);
		action->setCheckable(true);
		if (i == 3)
		{
			action->setMenu(subMenu);
		}
		menu->addAction(action);
	}

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The action in the menu has a sub menu, when you active this action, only show the sub menu, but can't be checked, why?