When a tear-off-enabled QMenu crosses multiple columns, the torn-off window resizes to the maximum and only shows one column

When a tear-off-enabled menu crosses multiple columns and the tear-off handle is activated, the independent window that's created goes haywire and gets resized until it reaches the absolute limits. Qt even spits out this message several times:

QWidget::setMinimumSize: (/QTornOffMenu) The largest allowed size is (16777215,16777215)

Which indicates it's doing something completely weird here.

Simple example code that should always trigger the bug is attached, derived from the official Qt 4.8.0 example 'menus', extended with a long (multi-column) tear-off menu. If your Y-resolution is so big / font size so small that the menu is displayed in one column you'd have to put more items in the menu (edit mainwindow.cpp, line 360).