New submission from Eric Wieser <wieser.eric+py...@gmail.com>: Discovered in https://github.com/numpy/numpy/pull/10882/files#r180813166
A reproduction: ``` In [1]: import ctypes In [2]: def make_array_ctype(shape): ...: import ctypes ...: ct = ctypes.c_uint8 ...: for i in shape: ...: ct = i * ct ...: return ct ...: # all on one line to keep ipython out of this In [3]: gc.collect(); x = make_array_ctype((1,)); del x; gc.collect() ``` Using the proposed function in https://github.com/numpy/numpy/pull/10891, we get a few more details: ``` In [4]: from numpy.testing import assert_no_gc_cycles In [5]: assert_no_gc_cycles(make_array_ctype, (1,)) AssertionError: Reference cycles were found when calling make_array_ctype: 7 objects were collected, of which 6 are shown below: tuple object with id=2822255556536: (<class '_ctypes.Array'>,) PyCArrayType object with id=2822226500408: <class '__main__.c_ubyte_Array_1'> getset_descriptor object with id=2822252062256: <attribute '__dict__' of 'c_ubyte_Array_1' objects> getset_descriptor object with id=2822252062184: <attribute '__weakref__' of 'c_ubyte_Array_1' objects> tuple object with id=2822243712440: (<class '__main__.c_ubyte_Array_1'>, <class '_ctypes.Array'>, <class '_ctypes._CData'>, <class 'object'>) StgDict object with id=2822226211928: {'__dict__': <attribute '__dict__' of 'c_ubyte_Array_1' objects>, '__doc__': None, '__module__': '__main__', '__weakref__': <attribute '__weakref__' of 'c_ubyte_Array_1' objects>, '_length_': 1, '_type_': <class 'ctypes.c_ubyte'>} ``` I suppose this isn't really a bug, but it's not clear to me why a cycle needs to be created here. ---------- components: ctypes messages: 315216 nosy: Eric.Wieser priority: normal severity: normal status: open title: ctypes array types create reference cycles versions: Python 3.5 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue33267> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
