[PyQt] Reference leak in QListView.setModel?

[Phil Thompson]

On Wed, 10 Sep 2008 16:59:04 +0000 (UTC), dfragi <daelfin at gmail.com> wrote:
> Hello,
> While trying to get rid of a memory leak in my program, I 
> tracked it down to this:
> 
> ##########################################################
> # 
> # import sys, gc
> # from PyQt4.Qt import *
> # 
> # class MyModel(QAbstractListModel):
> #     def rowCount(self, parent):
> #         return 5
> #     
> #     def data(self, index, role):
> #         if role == Qt.DisplayRole:
> #             return QVariant(str(index.row()))
> #         else:
> #             return QVariant()
> # 
> # def main():
> #     app = QApplication(sys.argv)
> #     
> #     model = MyModel()
> # 
> #     lv = QListView()
> #     print gc.get_referrers(model)
> #     lv.setModel(model)
> #     print gc.get_referrers(model)
> #     QApplication.processEvents()
> #     print gc.get_referrers(model)
> #     lv.setModel(None)
> #     print gc.get_referrers(model)    
> #     lv.show()
> # 
> #     app.exec_()
> # 
> # if __name__ == '__main__':
> #     main()
> ##########################################################
> 
> This outputs the following:
> 
> [<frame object at 0x8c7bd0>]
> [<frame object at 0x8c7bd0>]
> [<frame object at 0x8c7bd0>, 
>  <bound method MyModel.rowCount of <__main__.MyModel object at
0xd8f1e0>>,
>  <bound method MyModel.data of <__main__.MyModel object at 0xd8f1e0>>]
> [<frame object at 0x8c7bd0>, 
>  <bound method MyModel.rowCount of <__main__.MyModel object at
0xd8f1e0>>,
>  <bound method MyModel.data of <__main__.MyModel object at 0xd8f1e0>>]
> 
> i.e. after setModel(), the model isn't referenced anywhere else other
> than the current frame (the local name 'model'), which is ok. But after
> QApplication.processEvents, references to the bound methods rowCount() 
> and data() are being kept by PyQt, and not released even after the
> model is released. This keeps the model from being garbage-collected.
> 
> Is this a bug or should I be doing something differently?

This needs thinking about. Which means don't expect answer soon, but I
won't forget about it.

Phil