As the code comment says, ~QMainWindowTabBar will removeOne(this) from QMainWindowLayout::unusedTabBars. It doesn't assert that it was included in it, or something special like that. So we can optimize the whole thing by making sure that ~QMainWindowTabBar doesn't find anything to remove here, avoiding a detach from the copy 'bars' and potentially also avoiding quadratic behavior, as we delete the items in order. Found by Coverity, but it only saw this as an optimization opportunity because it doesn't understand that the copy is needed. Amends 23357e59bb4dc54e76a237b290aa64a620db2ea1. Pick-to: 6.5 Coverity-Id: 479705 Change-Id: I6c31e028c0c39813768e8c71076471b39bd8ef5a Reviewed-by: Axel Spoerl <axel.spoerl@qt.io> (cherry picked from commit fb7670f193712fae2d4c03d6ee2a6c30101b886f) Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org> (cherry picked from commit df8f7becfc38ad6441a7f409525c2becc1e3bf93)