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cpython/Lib/test/test_weakref.py
Tim Peters add09b4149 SF bug 840829: weakref callbacks and gc corrupt memory. 
subtype_dealloc():  This left the dying object exposed to gc, so that
if cyclic gc triggered during the weakref callback, gc tried to delete
the dying object a second time.  That's a disaster.  subtype_dealloc()
had a (I hope!) unique problem here, as every normal dealloc routine
untracks the object (from gc) before fiddling with weakrefs etc.  But
subtype_dealloc has obscure technical reasons for re-registering the
dying object with gc (already explained in a large comment block at
the bottom of the function).

The fix amounts to simply refraining from reregistering the dying object
with gc until after the weakref callback (if any) has been called.

This is a critical bug (hard to predict, and causes seemingly random
memory corruption when it occurs).  I'll backport it to 2.3 later.
2003-11-12 20:43:28 +00:00

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import sys
import unittest
import UserList
import weakref
from test import test_support
from sets import Set
class C:
def method(self):
pass
class Callable:
bar = None
def __call__(self, x):
self.bar = x
def create_function():
def f(): pass
return f
def create_bound_method():
return C().method
def create_unbound_method():
return C.method
class TestBase(unittest.TestCase):
def setUp(self):
self.cbcalled = 0
def callback(self, ref):
self.cbcalled += 1
class ReferencesTestCase(TestBase):
def test_basic_ref(self):
self.check_basic_ref(C)
self.check_basic_ref(create_function)
self.check_basic_ref(create_bound_method)
self.check_basic_ref(create_unbound_method)
# Just make sure the tp_repr handler doesn't raise an exception.
# Live reference:
o = C()
wr = weakref.ref(o)
`wr`
# Dead reference:
del o
`wr`
def test_basic_callback(self):
self.check_basic_callback(C)
self.check_basic_callback(create_function)
self.check_basic_callback(create_bound_method)
self.check_basic_callback(create_unbound_method)
def test_multiple_callbacks(self):
o = C()
ref1 = weakref.ref(o, self.callback)
ref2 = weakref.ref(o, self.callback)
del o
self.assert_(ref1() is None,
"expected reference to be invalidated")
self.assert_(ref2() is None,
"expected reference to be invalidated")
self.assert_(self.cbcalled == 2,
"callback not called the right number of times")
def test_multiple_selfref_callbacks(self):
# Make sure all references are invalidated before callbacks are called
#
# What's important here is that we're using the first
# reference in the callback invoked on the second reference
# (the most recently created ref is cleaned up first). This
# tests that all references to the object are invalidated
# before any of the callbacks are invoked, so that we only
# have one invocation of _weakref.c:cleanup_helper() active
# for a particular object at a time.
#
def callback(object, self=self):
self.ref()
c = C()
self.ref = weakref.ref(c, callback)
ref1 = weakref.ref(c, callback)
del c
def test_proxy_ref(self):
o = C()
o.bar = 1
ref1 = weakref.proxy(o, self.callback)
ref2 = weakref.proxy(o, self.callback)
del o
def check(proxy):
proxy.bar
self.assertRaises(weakref.ReferenceError, check, ref1)
self.assertRaises(weakref.ReferenceError, check, ref2)
self.assert_(self.cbcalled == 2)
def check_basic_ref(self, factory):
o = factory()
ref = weakref.ref(o)
self.assert_(ref() is not None,
"weak reference to live object should be live")
o2 = ref()
self.assert_(o is o2,
"<ref>() should return original object if live")
def check_basic_callback(self, factory):
self.cbcalled = 0
o = factory()
ref = weakref.ref(o, self.callback)
del o
self.assert_(self.cbcalled == 1,
"callback did not properly set 'cbcalled'")
self.assert_(ref() is None,
"ref2 should be dead after deleting object reference")
def test_ref_reuse(self):
o = C()
ref1 = weakref.ref(o)
# create a proxy to make sure that there's an intervening creation
# between these two; it should make no difference
proxy = weakref.proxy(o)
ref2 = weakref.ref(o)
self.assert_(ref1 is ref2,
"reference object w/out callback should be re-used")
o = C()
proxy = weakref.proxy(o)
ref1 = weakref.ref(o)
ref2 = weakref.ref(o)
self.assert_(ref1 is ref2,
"reference object w/out callback should be re-used")
self.assert_(weakref.getweakrefcount(o) == 2,
"wrong weak ref count for object")
del proxy
self.assert_(weakref.getweakrefcount(o) == 1,
"wrong weak ref count for object after deleting proxy")
def test_proxy_reuse(self):
o = C()
proxy1 = weakref.proxy(o)
ref = weakref.ref(o)
proxy2 = weakref.proxy(o)
self.assert_(proxy1 is proxy2,
"proxy object w/out callback should have been re-used")
def test_basic_proxy(self):
o = C()
self.check_proxy(o, weakref.proxy(o))
L = UserList.UserList()
p = weakref.proxy(L)
self.failIf(p, "proxy for empty UserList should be false")
p.append(12)
self.assertEqual(len(L), 1)
self.failUnless(p, "proxy for non-empty UserList should be true")
p[:] = [2, 3]
self.assertEqual(len(L), 2)
self.assertEqual(len(p), 2)
self.failUnless(3 in p,
"proxy didn't support __contains__() properly")
p[1] = 5
self.assertEqual(L[1], 5)
self.assertEqual(p[1], 5)
L2 = UserList.UserList(L)
p2 = weakref.proxy(L2)
self.assertEqual(p, p2)
## self.assertEqual(`L2`, `p2`)
L3 = UserList.UserList(range(10))
p3 = weakref.proxy(L3)
self.assertEqual(L3[:], p3[:])
self.assertEqual(L3[5:], p3[5:])
self.assertEqual(L3[:5], p3[:5])
self.assertEqual(L3[2:5], p3[2:5])
def test_callable_proxy(self):
o = Callable()
ref1 = weakref.proxy(o)
self.check_proxy(o, ref1)
self.assert_(type(ref1) is weakref.CallableProxyType,
"proxy is not of callable type")
ref1('twinkies!')
self.assert_(o.bar == 'twinkies!',
"call through proxy not passed through to original")
ref1(x='Splat.')
self.assert_(o.bar == 'Splat.',
"call through proxy not passed through to original")
# expect due to too few args
self.assertRaises(TypeError, ref1)
# expect due to too many args
self.assertRaises(TypeError, ref1, 1, 2, 3)
def check_proxy(self, o, proxy):
o.foo = 1
self.assert_(proxy.foo == 1,
"proxy does not reflect attribute addition")
o.foo = 2
self.assert_(proxy.foo == 2,
"proxy does not reflect attribute modification")
del o.foo
self.assert_(not hasattr(proxy, 'foo'),
"proxy does not reflect attribute removal")
proxy.foo = 1
self.assert_(o.foo == 1,
"object does not reflect attribute addition via proxy")
proxy.foo = 2
self.assert_(
o.foo == 2,
"object does not reflect attribute modification via proxy")
del proxy.foo
self.assert_(not hasattr(o, 'foo'),
"object does not reflect attribute removal via proxy")
def test_proxy_deletion(self):
# Test clearing of SF bug #762891
class Foo:
result = None
def __delitem__(self, accessor):
self.result = accessor
g = Foo()
f = weakref.proxy(g)
del f[0]
self.assertEqual(f.result, 0)
def test_getweakrefcount(self):
o = C()
ref1 = weakref.ref(o)
ref2 = weakref.ref(o, self.callback)
self.assert_(weakref.getweakrefcount(o) == 2,
"got wrong number of weak reference objects")
proxy1 = weakref.proxy(o)
proxy2 = weakref.proxy(o, self.callback)
self.assert_(weakref.getweakrefcount(o) == 4,
"got wrong number of weak reference objects")
def test_getweakrefs(self):
o = C()
ref1 = weakref.ref(o, self.callback)
ref2 = weakref.ref(o, self.callback)
del ref1
self.assert_(weakref.getweakrefs(o) == [ref2],
"list of refs does not match")
o = C()
ref1 = weakref.ref(o, self.callback)
ref2 = weakref.ref(o, self.callback)
del ref2
self.assert_(weakref.getweakrefs(o) == [ref1],
"list of refs does not match")
def test_newstyle_number_ops(self):
class F(float):
pass
f = F(2.0)
p = weakref.proxy(f)
self.assert_(p + 1.0 == 3.0)
self.assert_(1.0 + p == 3.0) # this used to SEGV
def test_callbacks_protected(self):
# Callbacks protected from already-set exceptions?
# Regression test for SF bug #478534.
class BogusError(Exception):
pass
data = {}
def remove(k):
del data[k]
def encapsulate():
f = lambda : ()
data[weakref.ref(f, remove)] = None
raise BogusError
try:
encapsulate()
except BogusError:
pass
else:
self.fail("exception not properly restored")
try:
encapsulate()
except BogusError:
pass
else:
self.fail("exception not properly restored")
def test_sf_bug_840829(self):
# "weakref callbacks and gc corrupt memory"
# subtype_dealloc erroneously exposed a new-style instance
# already in the process of getting deallocated to gc,
# causing double-deallocation if the instance had a weakref
# callback that triggered gc.
# If the bug exists, there probably won't be an obvious symptom
# in a release build. In a debug build, a segfault will occur
# when the second attempt to remove the instance from the "list
# of all objects" occurs.
import gc
class C(object):
pass
c = C()
wr = weakref.ref(c, lambda ignore: gc.collect())
del c
class Object:
def __init__(self, arg):
self.arg = arg
def __repr__(self):
return "<Object %r>" % self.arg
class MappingTestCase(TestBase):
COUNT = 10
def test_weak_values(self):
#
# This exercises d.copy(), d.items(), d[], del d[], len(d).
#
dict, objects = self.make_weak_valued_dict()
for o in objects:
self.assert_(weakref.getweakrefcount(o) == 1,
"wrong number of weak references to %r!" % o)
self.assert_(o is dict[o.arg],
"wrong object returned by weak dict!")
items1 = dict.items()
items2 = dict.copy().items()
items1.sort()
items2.sort()
self.assert_(items1 == items2,
"cloning of weak-valued dictionary did not work!")
del items1, items2
self.assert_(len(dict) == self.COUNT)
del objects[0]
self.assert_(len(dict) == (self.COUNT - 1),
"deleting object did not cause dictionary update")
del objects, o
self.assert_(len(dict) == 0,
"deleting the values did not clear the dictionary")
# regression on SF bug #447152:
dict = weakref.WeakValueDictionary()
self.assertRaises(KeyError, dict.__getitem__, 1)
dict[2] = C()
self.assertRaises(KeyError, dict.__getitem__, 2)
def test_weak_keys(self):
#
# This exercises d.copy(), d.items(), d[] = v, d[], del d[],
# len(d), d.has_key().
#
dict, objects = self.make_weak_keyed_dict()
for o in objects:
self.assert_(weakref.getweakrefcount(o) == 1,
"wrong number of weak references to %r!" % o)
self.assert_(o.arg is dict[o],
"wrong object returned by weak dict!")
items1 = dict.items()
items2 = dict.copy().items()
self.assert_(Set(items1) == Set(items2),
"cloning of weak-keyed dictionary did not work!")
del items1, items2
self.assert_(len(dict) == self.COUNT)
del objects[0]
self.assert_(len(dict) == (self.COUNT - 1),
"deleting object did not cause dictionary update")
del objects, o
self.assert_(len(dict) == 0,
"deleting the keys did not clear the dictionary")
o = Object(42)
dict[o] = "What is the meaning of the universe?"
self.assert_(dict.has_key(o))
self.assert_(not dict.has_key(34))
def test_weak_keyed_iters(self):
dict, objects = self.make_weak_keyed_dict()
self.check_iters(dict)
def test_weak_valued_iters(self):
dict, objects = self.make_weak_valued_dict()
self.check_iters(dict)
def check_iters(self, dict):
# item iterator:
items = dict.items()
for item in dict.iteritems():
items.remove(item)
self.assert_(len(items) == 0, "iteritems() did not touch all items")
# key iterator, via __iter__():
keys = dict.keys()
for k in dict:
keys.remove(k)
self.assert_(len(keys) == 0, "__iter__() did not touch all keys")
# key iterator, via iterkeys():
keys = dict.keys()
for k in dict.iterkeys():
keys.remove(k)
self.assert_(len(keys) == 0, "iterkeys() did not touch all keys")
# value iterator:
values = dict.values()
for v in dict.itervalues():
values.remove(v)
self.assert_(len(values) == 0,
"itervalues() did not touch all values")
def test_make_weak_keyed_dict_from_dict(self):
o = Object(3)
dict = weakref.WeakKeyDictionary({o:364})
self.assert_(dict[o] == 364)
def test_make_weak_keyed_dict_from_weak_keyed_dict(self):
o = Object(3)
dict = weakref.WeakKeyDictionary({o:364})
dict2 = weakref.WeakKeyDictionary(dict)
self.assert_(dict[o] == 364)
def make_weak_keyed_dict(self):
dict = weakref.WeakKeyDictionary()
objects = map(Object, range(self.COUNT))
for o in objects:
dict[o] = o.arg
return dict, objects
def make_weak_valued_dict(self):
dict = weakref.WeakValueDictionary()
objects = map(Object, range(self.COUNT))
for o in objects:
dict[o.arg] = o
return dict, objects
def check_popitem(self, klass, key1, value1, key2, value2):
weakdict = klass()
weakdict[key1] = value1
weakdict[key2] = value2
self.assert_(len(weakdict) == 2)
k, v = weakdict.popitem()
self.assert_(len(weakdict) == 1)
if k is key1:
self.assert_(v is value1)
else:
self.assert_(v is value2)
k, v = weakdict.popitem()
self.assert_(len(weakdict) == 0)
if k is key1:
self.assert_(v is value1)
else:
self.assert_(v is value2)
def test_weak_valued_dict_popitem(self):
self.check_popitem(weakref.WeakValueDictionary,
"key1", C(), "key2", C())
def test_weak_keyed_dict_popitem(self):
self.check_popitem(weakref.WeakKeyDictionary,
C(), "value 1", C(), "value 2")
def check_setdefault(self, klass, key, value1, value2):
self.assert_(value1 is not value2,
"invalid test"
" -- value parameters must be distinct objects")
weakdict = klass()
o = weakdict.setdefault(key, value1)
self.assert_(o is value1)
self.assert_(weakdict.has_key(key))
self.assert_(weakdict.get(key) is value1)
self.assert_(weakdict[key] is value1)
o = weakdict.setdefault(key, value2)
self.assert_(o is value1)
self.assert_(weakdict.has_key(key))
self.assert_(weakdict.get(key) is value1)
self.assert_(weakdict[key] is value1)
def test_weak_valued_dict_setdefault(self):
self.check_setdefault(weakref.WeakValueDictionary,
"key", C(), C())
def test_weak_keyed_dict_setdefault(self):
self.check_setdefault(weakref.WeakKeyDictionary,
C(), "value 1", "value 2")
def check_update(self, klass, dict):
#
# This exercises d.update(), len(d), d.keys(), d.has_key(),
# d.get(), d[].
#
weakdict = klass()
weakdict.update(dict)
self.assert_(len(weakdict) == len(dict))
for k in weakdict.keys():
self.assert_(dict.has_key(k),
"mysterious new key appeared in weak dict")
v = dict.get(k)
self.assert_(v is weakdict[k])
self.assert_(v is weakdict.get(k))
for k in dict.keys():
self.assert_(weakdict.has_key(k),
"original key disappeared in weak dict")
v = dict[k]
self.assert_(v is weakdict[k])
self.assert_(v is weakdict.get(k))
def test_weak_valued_dict_update(self):
self.check_update(weakref.WeakValueDictionary,
{1: C(), 'a': C(), C(): C()})
def test_weak_keyed_dict_update(self):
self.check_update(weakref.WeakKeyDictionary,
{C(): 1, C(): 2, C(): 3})
def test_weak_keyed_delitem(self):
d = weakref.WeakKeyDictionary()
o1 = Object('1')
o2 = Object('2')
d[o1] = 'something'
d[o2] = 'something'
self.assert_(len(d) == 2)
del d[o1]
self.assert_(len(d) == 1)
self.assert_(d.keys() == [o2])
def test_weak_valued_delitem(self):
d = weakref.WeakValueDictionary()
o1 = Object('1')
o2 = Object('2')
d['something'] = o1
d['something else'] = o2
self.assert_(len(d) == 2)
del d['something']
self.assert_(len(d) == 1)
self.assert_(d.items() == [('something else', o2)])
def test_weak_keyed_bad_delitem(self):
d = weakref.WeakKeyDictionary()
o = Object('1')
# An attempt to delete an object that isn't there should raise
# KeyError. It didn't before 2.3.
self.assertRaises(KeyError, d.__delitem__, o)
self.assertRaises(KeyError, d.__getitem__, o)
# If a key isn't of a weakly referencable type, __getitem__ and
# __setitem__ raise TypeError. __delitem__ should too.
self.assertRaises(TypeError, d.__delitem__, 13)
self.assertRaises(TypeError, d.__getitem__, 13)
self.assertRaises(TypeError, d.__setitem__, 13, 13)
def test_weak_keyed_cascading_deletes(self):
# SF bug 742860. For some reason, before 2.3 __delitem__ iterated
# over the keys via self.data.iterkeys(). If things vanished from
# the dict during this (or got added), that caused a RuntimeError.
d = weakref.WeakKeyDictionary()
mutate = False
class C(object):
def __init__(self, i):
self.value = i
def __hash__(self):
return hash(self.value)
def __eq__(self, other):
if mutate:
# Side effect that mutates the dict, by removing the
# last strong reference to a key.
del objs[-1]
return self.value == other.value
objs = [C(i) for i in range(4)]
for o in objs:
d[o] = o.value
del o # now the only strong references to keys are in objs
# Find the order in which iterkeys sees the keys.
objs = d.keys()
# Reverse it, so that the iteration implementation of __delitem__
# has to keep looping to find the first object we delete.
objs.reverse()
# Turn on mutation in C.__eq__. The first time thru the loop,
# under the iterkeys() business the first comparison will delete
# the last item iterkeys() would see, and that causes a
# RuntimeError: dictionary changed size during iteration
# when the iterkeys() loop goes around to try comparing the next
# key. After this was fixed, it just deletes the last object *our*
# "for o in obj" loop would have gotten to.
mutate = True
count = 0
for o in objs:
count += 1
del d[o]
self.assertEqual(len(d), 0)
self.assertEqual(count, 2)
from test_userdict import TestMappingProtocol
class WeakValueDictionaryTestCase(TestMappingProtocol):
"""Check that WeakValueDictionary conforms to the mapping protocol"""
__ref = {"key1":Object(1), "key2":Object(2), "key3":Object(3)}
_tested_class = weakref.WeakValueDictionary
def _reference(self):
return self.__ref.copy()
class WeakKeyDictionaryTestCase(TestMappingProtocol):
"""Check that WeakKeyDictionary conforms to the mapping protocol"""
__ref = {Object("key1"):1, Object("key2"):2, Object("key3"):3}
_tested_class = weakref.WeakKeyDictionary
def _reference(self):
return self.__ref.copy()
def test_main():
test_support.run_unittest(
ReferencesTestCase,
MappingTestCase,
WeakValueDictionaryTestCase,
WeakKeyDictionaryTestCase,
)
if __name__ == "__main__":
test_main()
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