From 52c424343d625d3e795bd670aaaf542dfa63b7c7 Mon Sep 17 00:00:00 2001 From: Benjamin Peterson Date: Wed, 7 Mar 2012 18:41:11 -0600 Subject: [PATCH] allow cycles throught the __dict__ slot to be cleared (closes #1469629) Patch from Armin, test from me. --- Lib/test/test_descr.py | 19 +++++++++++++++++-- Misc/NEWS | 3 +++ Objects/typeobject.c | 9 +++++++-- 3 files changed, 27 insertions(+), 4 deletions(-) diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py index 92304b4e7ef..4aeb77fd0f2 100644 --- a/Lib/test/test_descr.py +++ b/Lib/test/test_descr.py @@ -1,8 +1,10 @@ import builtins +import gc import sys import types import math import unittest +import weakref from copy import deepcopy from test import support @@ -1186,7 +1188,6 @@ order (MRO) for bases """ self.assertEqual(Counted.counter, 0) # Test lookup leaks [SF bug 572567] - import gc if hasattr(gc, 'get_objects'): class G(object): def __eq__(self, other): @@ -4380,7 +4381,6 @@ order (MRO) for bases """ self.assertRaises(AttributeError, getattr, C(), "attr") self.assertEqual(descr.counter, 4) - import gc class EvilGetattribute(object): # This used to segfault def __getattr__(self, name): @@ -4429,6 +4429,21 @@ order (MRO) for bases """ foo = Foo() str(foo) + def test_cycle_through_dict(self): + # See bug #1469629 + class X(dict): + def __init__(self): + dict.__init__(self) + self.__dict__ = self + x = X() + x.attr = 42 + wr = weakref.ref(x) + del x + support.gc_collect() + self.assertIsNone(wr()) + for o in gc.get_objects(): + self.assertIsNot(type(o), X) + class DictProxyTests(unittest.TestCase): def setUp(self): class C(object): diff --git a/Misc/NEWS b/Misc/NEWS index 44683f5d5f3..119dfd71bfb 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -10,6 +10,9 @@ What's New in Python 3.2.3 release candidate 1? Core and Builtins ----------------- +- Issue #1469629: Allow cycles through an object's __dict__ slot to be + collected. (For example if ``x.__dict__ is x``). + - Issue #14172: Fix reference leak when marshalling a buffer-like object (other than a bytes object). diff --git a/Objects/typeobject.c b/Objects/typeobject.c index c3822abb0e0..e0066948059 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -830,8 +830,13 @@ subtype_clear(PyObject *self) assert(base); } - /* There's no need to clear the instance dict (if any); - the collector will call its tp_clear handler. */ + /* Clear the instance dict (if any), to break cycles involving only + __dict__ slots (as in the case 'self.__dict__ is self'). */ + if (type->tp_dictoffset != base->tp_dictoffset) { + PyObject **dictptr = _PyObject_GetDictPtr(self); + if (dictptr && *dictptr) + Py_CLEAR(*dictptr); + } if (baseclear) return baseclear(self);