Use weakrefs to hold onto classes #2521.
This also causes the _weakref module to be built into the core.
diff --git a/Lib/abc.py b/Lib/abc.py
index 515ba08..02e48a1 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -5,6 +5,7 @@
import types
+from _weakrefset import WeakSet
# Instance of old-style class
class _C: pass
@@ -95,9 +96,9 @@
abstracts.add(name)
cls.__abstractmethods__ = frozenset(abstracts)
# Set up inheritance registry
- cls._abc_registry = set()
- cls._abc_cache = set()
- cls._abc_negative_cache = set()
+ cls._abc_registry = WeakSet()
+ cls._abc_cache = WeakSet()
+ cls._abc_negative_cache = WeakSet()
cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
return cls
@@ -128,7 +129,7 @@
"""Override for isinstance(instance, cls)."""
# Inline the cache checking when it's simple.
subclass = getattr(instance, '__class__', None)
- if subclass in cls._abc_cache:
+ if subclass is not None and subclass in cls._abc_cache:
return True
subtype = type(instance)
# Old-style instances
@@ -152,7 +153,7 @@
# Check negative cache; may have to invalidate
if cls._abc_negative_cache_version < ABCMeta._abc_invalidation_counter:
# Invalidate the negative cache
- cls._abc_negative_cache = set()
+ cls._abc_negative_cache = WeakSet()
cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
elif subclass in cls._abc_negative_cache:
return False
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index b5af46b..6a8c3a1 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -3,7 +3,7 @@
"""Unit tests for abc.py."""
-import unittest
+import unittest, weakref
from test import test_support
import abc
@@ -208,6 +208,22 @@
C()
self.assertEqual(B.counter, 1)
+ def test_cache_leak(self):
+ # See issue #2521.
+ class A(object):
+ __metaclass__ = abc.ABCMeta
+ @abc.abstractmethod
+ def f(self):
+ pass
+ class C(A):
+ def f(self):
+ A.f(self)
+ r = weakref.ref(C)
+ # Trigger cache.
+ C().f()
+ del C
+ test_support.gc_collect()
+ self.assertEqual(r(), None)
def test_main():
test_support.run_unittest(TestABC)
diff --git a/Misc/NEWS b/Misc/NEWS
index 29bc276..349cc7f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -31,6 +31,9 @@
Library
-------
+- Issue #2521: Use weakrefs on for caching in the abc module, so that classes
+ are not held onto after they are deleted elsewhere.
+
- Issue #9626: the view methods for collections.OrderedDict() were returning
the unordered versions inherited from dict. Those methods are now
overridden to provide ordered views.
@@ -188,6 +191,9 @@
Extension Modules
-----------------
+- As a result of issue #2521, the _weakref module is now compiled into the
+ interpreter by default.
+
- Issue #9324: Add parameter validation to signal.signal on Windows in order
to prevent crashes.
diff --git a/Modules/Setup.dist b/Modules/Setup.dist
index e76e0df..e2b0c59 100644
--- a/Modules/Setup.dist
+++ b/Modules/Setup.dist
@@ -118,6 +118,7 @@
# if $HOME is not set
_sre _sre.c # Fredrik Lundh's new regular expressions
_codecs _codecsmodule.c # access to the builtin codecs and codec registry
+_weakref _weakref.c # weak references
# The zipimport module is always imported at startup. Having it as a
# builtin module avoids some bootstrapping problems and reduces overhead.