这个一个Qt4.7的一个bug，你可以去vote
https://bugreports.qt.nokia.com/browse/QTBUG-22817来增强Qt官方对此bug的重视程度
bug的修复相对来说比较容易，只需要修改Qt源码中的一行代码即可。详细信息见
http://blog.csdn.net/dbzhang800/article/details/6990026对于Qt4.8/Qt5.0，我已经提交的merge request，但是Qt Widget现在几乎处于无人管理的状态，所以何时修复是一个未知数。
From Qt4.7 on, the contextmenu of
QTextEdit/QPlainTextEdit/QLineEdit/QLabel/QMainWindow etc using
QMenu::popup() instead of QMenu::exec(), but the
setAttribute(Qt::WA_DeleteOnClose) does not work, as QMenu::close()
isn't called when the menus disapper. And this causes a memory leak.
This is a side effect of b7af368e86874d71ffc9071c9ef009814d6a3467
