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Copy pathtest_weakref.py
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2246 lines (1935 loc) · 74.3 KB
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import gc
import sys
import doctest
import unittest
import collections
import weakref
import operator
import contextlib
import copy
import threading
import time
import random
from test import support
from test.support import script_helper, ALWAYS_EQ
from test.support import gc_collect
from test.support import threading_helper
# Used in ReferencesTestCase.test_ref_created_during_del() .
ref_from_del = None
# Used by FinalizeTestCase as a global that may be replaced by None
# when the interpreter shuts down.
_global_var = 'foobar'
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
class Object:
def __init__(self, arg):
self.arg = arg
def __repr__(self):
return "<Object %r>" % self.arg
def __eq__(self, other):
if isinstance(other, Object):
return self.arg == other.arg
return NotImplemented
def __lt__(self, other):
if isinstance(other, Object):
return self.arg < other.arg
return NotImplemented
def __hash__(self):
return hash(self.arg)
def some_method(self):
return 4
def other_method(self):
return 5
class RefCycle:
def __init__(self):
self.cycle = self
class TestBase(unittest.TestCase):
def setUp(self):
self.cbcalled = 0
def callback(self, ref):
self.cbcalled += 1
@contextlib.contextmanager
def collect_in_thread(period=0.0001):
"""
Ensure GC collections happen in a different thread, at a high frequency.
"""
please_stop = False
def collect():
while not please_stop:
time.sleep(period)
gc.collect()
with support.disable_gc():
t = threading.Thread(target=collect)
t.start()
try:
yield
finally:
please_stop = True
t.join()
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)
# Just make sure the tp_repr handler doesn't raise an exception.
# Live reference:
o = C()
wr = weakref.ref(o)
repr(wr)
# Dead reference:
del o
repr(wr)
def test_repr_failure_gh99184(self):
class MyConfig(dict):
def __getattr__(self, x):
return self[x]
obj = MyConfig(offset=5)
obj_weakref = weakref.ref(obj)
self.assertIn('MyConfig', repr(obj_weakref))
self.assertIn('MyConfig', str(obj_weakref))
def test_basic_callback(self):
self.check_basic_callback(C)
self.check_basic_callback(create_function)
self.check_basic_callback(create_bound_method)
@support.cpython_only
def test_cfunction(self):
import _testcapi
create_cfunction = _testcapi.create_cfunction
f = create_cfunction()
wr = weakref.ref(f)
self.assertIs(wr(), f)
del f
self.assertIsNone(wr())
self.check_basic_ref(create_cfunction)
self.check_basic_callback(create_cfunction)
def test_multiple_callbacks(self):
o = C()
ref1 = weakref.ref(o, self.callback)
ref2 = weakref.ref(o, self.callback)
del o
gc_collect() # For PyPy or other GCs.
self.assertIsNone(ref1(), "expected reference to be invalidated")
self.assertIsNone(ref2(), "expected reference to be invalidated")
self.assertEqual(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_constructor_kwargs(self):
c = C()
self.assertRaises(TypeError, weakref.ref, c, callback=None)
def test_proxy_ref(self):
o = C()
o.bar = 1
ref1 = weakref.proxy(o, self.callback)
ref2 = weakref.proxy(o, self.callback)
del o
gc_collect() # For PyPy or other GCs.
def check(proxy):
proxy.bar
self.assertRaises(ReferenceError, check, ref1)
self.assertRaises(ReferenceError, check, ref2)
ref3 = weakref.proxy(C())
gc_collect() # For PyPy or other GCs.
self.assertRaises(ReferenceError, bool, ref3)
self.assertEqual(self.cbcalled, 2)
def check_basic_ref(self, factory):
o = factory()
ref = weakref.ref(o)
self.assertIsNotNone(ref(),
"weak reference to live object should be live")
o2 = ref()
self.assertIs(o, 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
gc_collect() # For PyPy or other GCs.
self.assertEqual(self.cbcalled, 1,
"callback did not properly set 'cbcalled'")
self.assertIsNone(ref(),
"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.assertIs(ref1, 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.assertIs(ref1, ref2,
"reference object w/out callback should be re-used")
self.assertEqual(weakref.getweakrefcount(o), 2,
"wrong weak ref count for object")
del proxy
gc_collect() # For PyPy or other GCs.
self.assertEqual(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.assertIs(proxy1, 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 = collections.UserList()
p = weakref.proxy(L)
self.assertFalse(p, "proxy for empty UserList should be false")
p.append(12)
self.assertEqual(len(L), 1)
self.assertTrue(p, "proxy for non-empty UserList should be true")
p[:] = [2, 3]
self.assertEqual(len(L), 2)
self.assertEqual(len(p), 2)
self.assertIn(3, p, "proxy didn't support __contains__() properly")
p[1] = 5
self.assertEqual(L[1], 5)
self.assertEqual(p[1], 5)
L2 = collections.UserList(L)
p2 = weakref.proxy(L2)
self.assertEqual(p, p2)
## self.assertEqual(repr(L2), repr(p2))
L3 = collections.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_proxy_unicode(self):
# See bug 5037
class C(object):
def __str__(self):
return "string"
def __bytes__(self):
return b"bytes"
instance = C()
self.assertIn("__bytes__", dir(weakref.proxy(instance)))
self.assertEqual(bytes(weakref.proxy(instance)), b"bytes")
def test_proxy_index(self):
class C:
def __index__(self):
return 10
o = C()
p = weakref.proxy(o)
self.assertEqual(operator.index(p), 10)
def test_proxy_div(self):
class C:
def __floordiv__(self, other):
return 42
def __ifloordiv__(self, other):
return 21
o = C()
p = weakref.proxy(o)
self.assertEqual(p // 5, 42)
p //= 5
self.assertEqual(p, 21)
def test_proxy_matmul(self):
class C:
def __matmul__(self, other):
return 1729
def __rmatmul__(self, other):
return -163
def __imatmul__(self, other):
return 561
o = C()
p = weakref.proxy(o)
self.assertEqual(p @ 5, 1729)
self.assertEqual(5 @ p, -163)
p @= 5
self.assertEqual(p, 561)
# The PyWeakref_* C API is documented as allowing either NULL or
# None as the value for the callback, where either means "no
# callback". The "no callback" ref and proxy objects are supposed
# to be shared so long as they exist by all callers so long as
# they are active. In Python 2.3.3 and earlier, this guarantee
# was not honored, and was broken in different ways for
# PyWeakref_NewRef() and PyWeakref_NewProxy(). (Two tests.)
def test_shared_ref_without_callback(self):
self.check_shared_without_callback(weakref.ref)
def test_shared_proxy_without_callback(self):
self.check_shared_without_callback(weakref.proxy)
def check_shared_without_callback(self, makeref):
o = Object(1)
p1 = makeref(o, None)
p2 = makeref(o, None)
self.assertIs(p1, p2, "both callbacks were None in the C API")
del p1, p2
p1 = makeref(o)
p2 = makeref(o, None)
self.assertIs(p1, p2, "callbacks were NULL, None in the C API")
del p1, p2
p1 = makeref(o)
p2 = makeref(o)
self.assertIs(p1, p2, "both callbacks were NULL in the C API")
del p1, p2
p1 = makeref(o, None)
p2 = makeref(o)
self.assertIs(p1, p2, "callbacks were None, NULL in the C API")
def test_callable_proxy(self):
o = Callable()
ref1 = weakref.proxy(o)
self.check_proxy(o, ref1)
self.assertIs(type(ref1), weakref.CallableProxyType,
"proxy is not of callable type")
ref1('twinkies!')
self.assertEqual(o.bar, 'twinkies!',
"call through proxy not passed through to original")
ref1(x='Splat.')
self.assertEqual(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.assertEqual(proxy.foo, 1,
"proxy does not reflect attribute addition")
o.foo = 2
self.assertEqual(proxy.foo, 2,
"proxy does not reflect attribute modification")
del o.foo
self.assertFalse(hasattr(proxy, 'foo'),
"proxy does not reflect attribute removal")
proxy.foo = 1
self.assertEqual(o.foo, 1,
"object does not reflect attribute addition via proxy")
proxy.foo = 2
self.assertEqual(o.foo, 2,
"object does not reflect attribute modification via proxy")
del proxy.foo
self.assertFalse(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_proxy_bool(self):
# Test clearing of SF bug #1170766
class List(list): pass
lyst = List()
self.assertEqual(bool(weakref.proxy(lyst)), bool(lyst))
def test_proxy_iter(self):
# Test fails with a debug build of the interpreter
# (see bpo-38395).
obj = None
class MyObj:
def __iter__(self):
nonlocal obj
del obj
return NotImplemented
obj = MyObj()
p = weakref.proxy(obj)
with self.assertRaises(TypeError):
# "blech" in p calls MyObj.__iter__ through the proxy,
# without keeping a reference to the real object, so it
# can be killed in the middle of the call
"blech" in p
def test_proxy_next(self):
arr = [4, 5, 6]
def iterator_func():
yield from arr
it = iterator_func()
class IteratesWeakly:
def __iter__(self):
return weakref.proxy(it)
weak_it = IteratesWeakly()
# Calls proxy.__next__
self.assertEqual(list(weak_it), [4, 5, 6])
def test_proxy_bad_next(self):
# bpo-44720: PyIter_Next() shouldn't be called if the reference
# isn't an iterator.
not_an_iterator = lambda: 0
class A:
def __iter__(self):
return weakref.proxy(not_an_iterator)
a = A()
msg = "Weakref proxy referenced a non-iterator"
with self.assertRaisesRegex(TypeError, msg):
list(a)
def test_proxy_reversed(self):
class MyObj:
def __len__(self):
return 3
def __reversed__(self):
return iter('cba')
obj = MyObj()
self.assertEqual("".join(reversed(weakref.proxy(obj))), "cba")
def test_proxy_hash(self):
class MyObj:
def __hash__(self):
return 42
obj = MyObj()
with self.assertRaises(TypeError):
hash(weakref.proxy(obj))
class MyObj:
__hash__ = None
obj = MyObj()
with self.assertRaises(TypeError):
hash(weakref.proxy(obj))
def test_getweakrefcount(self):
o = C()
ref1 = weakref.ref(o)
ref2 = weakref.ref(o, self.callback)
self.assertEqual(weakref.getweakrefcount(o), 2,
"got wrong number of weak reference objects")
proxy1 = weakref.proxy(o)
proxy2 = weakref.proxy(o, self.callback)
self.assertEqual(weakref.getweakrefcount(o), 4,
"got wrong number of weak reference objects")
del ref1, ref2, proxy1, proxy2
gc_collect() # For PyPy or other GCs.
self.assertEqual(weakref.getweakrefcount(o), 0,
"weak reference objects not unlinked from"
" referent when discarded.")
# assumes ints do not support weakrefs
self.assertEqual(weakref.getweakrefcount(1), 0,
"got wrong number of weak reference objects for int")
def test_getweakrefs(self):
o = C()
ref1 = weakref.ref(o, self.callback)
ref2 = weakref.ref(o, self.callback)
del ref1
gc_collect() # For PyPy or other GCs.
self.assertEqual(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
gc_collect() # For PyPy or other GCs.
self.assertEqual(weakref.getweakrefs(o), [ref1],
"list of refs does not match")
del ref1
gc_collect() # For PyPy or other GCs.
self.assertEqual(weakref.getweakrefs(o), [],
"list of refs not cleared")
# assumes ints do not support weakrefs
self.assertEqual(weakref.getweakrefs(1), [],
"list of refs does not match for int")
def test_newstyle_number_ops(self):
class F(float):
pass
f = F(2.0)
p = weakref.proxy(f)
self.assertEqual(p + 1.0, 3.0)
self.assertEqual(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
# There endeth the first part. It gets worse.
del wr
c1 = C()
c1.i = C()
wr = weakref.ref(c1.i, lambda ignore: gc.collect())
c2 = C()
c2.c1 = c1
del c1 # still alive because c2 points to it
# Now when subtype_dealloc gets called on c2, it's not enough just
# that c2 is immune from gc while the weakref callbacks associated
# with c2 execute (there are none in this 2nd half of the test, btw).
# subtype_dealloc goes on to call the base classes' deallocs too,
# so any gc triggered by weakref callbacks associated with anything
# torn down by a base class dealloc can also trigger double
# deallocation of c2.
del c2
def test_callback_in_cycle(self):
import gc
class J(object):
pass
class II(object):
def acallback(self, ignore):
self.J
I = II()
I.J = J
I.wr = weakref.ref(J, I.acallback)
# Now J and II are each in a self-cycle (as all new-style class
# objects are, since their __mro__ points back to them). I holds
# both a weak reference (I.wr) and a strong reference (I.J) to class
# J. I is also in a cycle (I.wr points to a weakref that references
# I.acallback). When we del these three, they all become trash, but
# the cycles prevent any of them from getting cleaned up immediately.
# Instead they have to wait for cyclic gc to deduce that they're
# trash.
#
# gc used to call tp_clear on all of them, and the order in which
# it does that is pretty accidental. The exact order in which we
# built up these things manages to provoke gc into running tp_clear
# in just the right order (I last). Calling tp_clear on II leaves
# behind an insane class object (its __mro__ becomes NULL). Calling
# tp_clear on J breaks its self-cycle, but J doesn't get deleted
# just then because of the strong reference from I.J. Calling
# tp_clear on I starts to clear I's __dict__, and just happens to
# clear I.J first -- I.wr is still intact. That removes the last
# reference to J, which triggers the weakref callback. The callback
# tries to do "self.J", and instances of new-style classes look up
# attributes ("J") in the class dict first. The class (II) wants to
# search II.__mro__, but that's NULL. The result was a segfault in
# a release build, and an assert failure in a debug build.
del I, J, II
gc.collect()
def test_callback_reachable_one_way(self):
import gc
# This one broke the first patch that fixed the previous test. In this case,
# the objects reachable from the callback aren't also reachable
# from the object (c1) *triggering* the callback: you can get to
# c1 from c2, but not vice-versa. The result was that c2's __dict__
# got tp_clear'ed by the time the c2.cb callback got invoked.
class C:
def cb(self, ignore):
self.me
self.c1
self.wr
c1, c2 = C(), C()
c2.me = c2
c2.c1 = c1
c2.wr = weakref.ref(c1, c2.cb)
del c1, c2
gc.collect()
def test_callback_different_classes(self):
import gc
# Like test_callback_reachable_one_way, except c2 and c1 have different
# classes. c2's class (C) isn't reachable from c1 then, so protecting
# objects reachable from the dying object (c1) isn't enough to stop
# c2's class (C) from getting tp_clear'ed before c2.cb is invoked.
# The result was a segfault (C.__mro__ was NULL when the callback
# tried to look up self.me).
class C(object):
def cb(self, ignore):
self.me
self.c1
self.wr
class D:
pass
c1, c2 = D(), C()
c2.me = c2
c2.c1 = c1
c2.wr = weakref.ref(c1, c2.cb)
del c1, c2, C, D
gc.collect()
def test_callback_in_cycle_resurrection(self):
import gc
# Do something nasty in a weakref callback: resurrect objects
# from dead cycles. For this to be attempted, the weakref and
# its callback must also be part of the cyclic trash (else the
# objects reachable via the callback couldn't be in cyclic trash
# to begin with -- the callback would act like an external root).
# But gc clears trash weakrefs with callbacks early now, which
# disables the callbacks, so the callbacks shouldn't get called
# at all (and so nothing actually gets resurrected).
alist = []
class C(object):
def __init__(self, value):
self.attribute = value
def acallback(self, ignore):
alist.append(self.c)
c1, c2 = C(1), C(2)
c1.c = c2
c2.c = c1
c1.wr = weakref.ref(c2, c1.acallback)
c2.wr = weakref.ref(c1, c2.acallback)
def C_went_away(ignore):
alist.append("C went away")
wr = weakref.ref(C, C_went_away)
del c1, c2, C # make them all trash
self.assertEqual(alist, []) # del isn't enough to reclaim anything
gc.collect()
# c1.wr and c2.wr were part of the cyclic trash, so should have
# been cleared without their callbacks executing. OTOH, the weakref
# to C is bound to a function local (wr), and wasn't trash, so that
# callback should have been invoked when C went away.
self.assertEqual(alist, ["C went away"])
# The remaining weakref should be dead now (its callback ran).
self.assertEqual(wr(), None)
del alist[:]
gc.collect()
self.assertEqual(alist, [])
def test_callbacks_on_callback(self):
import gc
# Set up weakref callbacks *on* weakref callbacks.
alist = []
def safe_callback(ignore):
alist.append("safe_callback called")
class C(object):
def cb(self, ignore):
alist.append("cb called")
c, d = C(), C()
c.other = d
d.other = c
callback = c.cb
c.wr = weakref.ref(d, callback) # this won't trigger
d.wr = weakref.ref(callback, d.cb) # ditto
external_wr = weakref.ref(callback, safe_callback) # but this will
self.assertIs(external_wr(), callback)
# The weakrefs attached to c and d should get cleared, so that
# C.cb is never called. But external_wr isn't part of the cyclic
# trash, and no cyclic trash is reachable from it, so safe_callback
# should get invoked when the bound method object callback (c.cb)
# -- which is itself a callback, and also part of the cyclic trash --
# gets reclaimed at the end of gc.
del callback, c, d, C
self.assertEqual(alist, []) # del isn't enough to clean up cycles
gc.collect()
self.assertEqual(alist, ["safe_callback called"])
self.assertEqual(external_wr(), None)
del alist[:]
gc.collect()
self.assertEqual(alist, [])
def test_gc_during_ref_creation(self):
self.check_gc_during_creation(weakref.ref)
def test_gc_during_proxy_creation(self):
self.check_gc_during_creation(weakref.proxy)
def check_gc_during_creation(self, makeref):
thresholds = gc.get_threshold()
gc.set_threshold(1, 1, 1)
gc.collect()
class A:
pass
def callback(*args):
pass
referenced = A()
a = A()
a.a = a
a.wr = makeref(referenced)
try:
# now make sure the object and the ref get labeled as
# cyclic trash:
a = A()
weakref.ref(referenced, callback)
finally:
gc.set_threshold(*thresholds)
def test_ref_created_during_del(self):
# Bug #1377858
# A weakref created in an object's __del__() would crash the
# interpreter when the weakref was cleaned up since it would refer to
# non-existent memory. This test should not segfault the interpreter.
class Target(object):
def __del__(self):
global ref_from_del
ref_from_del = weakref.ref(self)
w = Target()
def test_init(self):
# Issue 3634
# <weakref to class>.__init__() doesn't check errors correctly
r = weakref.ref(Exception)
self.assertRaises(TypeError, r.__init__, 0, 0, 0, 0, 0)
# No exception should be raised here
gc.collect()
def test_classes(self):
# Check that classes are weakrefable.
class A(object):
pass
l = []
weakref.ref(int)
a = weakref.ref(A, l.append)
A = None
gc.collect()
self.assertEqual(a(), None)
self.assertEqual(l, [a])
def test_equality(self):
# Alive weakrefs defer equality testing to their underlying object.
x = Object(1)
y = Object(1)
z = Object(2)
a = weakref.ref(x)
b = weakref.ref(y)
c = weakref.ref(z)
d = weakref.ref(x)
# Note how we directly test the operators here, to stress both
# __eq__ and __ne__.
self.assertTrue(a == b)
self.assertFalse(a != b)
self.assertFalse(a == c)
self.assertTrue(a != c)
self.assertTrue(a == d)
self.assertFalse(a != d)
self.assertFalse(a == x)
self.assertTrue(a != x)
self.assertTrue(a == ALWAYS_EQ)
self.assertFalse(a != ALWAYS_EQ)
del x, y, z
gc.collect()
for r in a, b, c:
# Sanity check
self.assertIs(r(), None)
# Dead weakrefs compare by identity: whether `a` and `d` are the
# same weakref object is an implementation detail, since they pointed
# to the same original object and didn't have a callback.
# (see issue #16453).
self.assertFalse(a == b)
self.assertTrue(a != b)
self.assertFalse(a == c)
self.assertTrue(a != c)
self.assertEqual(a == d, a is d)
self.assertEqual(a != d, a is not d)
def test_ordering(self):
# weakrefs cannot be ordered, even if the underlying objects can.
ops = [operator.lt, operator.gt, operator.le, operator.ge]
x = Object(1)
y = Object(1)
a = weakref.ref(x)
b = weakref.ref(y)
for op in ops:
self.assertRaises(TypeError, op, a, b)
# Same when dead.
del x, y
gc.collect()
for op in ops:
self.assertRaises(TypeError, op, a, b)
def test_hashing(self):
# Alive weakrefs hash the same as the underlying object
x = Object(42)
y = Object(42)
a = weakref.ref(x)
b = weakref.ref(y)
self.assertEqual(hash(a), hash(42))
del x, y
gc.collect()
# Dead weakrefs:
# - retain their hash is they were hashed when alive;
# - otherwise, cannot be hashed.
self.assertEqual(hash(a), hash(42))
self.assertRaises(TypeError, hash, b)
def test_trashcan_16602(self):
# Issue #16602: when a weakref's target was part of a long
# deallocation chain, the trashcan mechanism could delay clearing
# of the weakref and make the target object visible from outside
# code even though its refcount had dropped to 0. A crash ensued.
class C:
def __init__(self, parent):
if not parent:
return
wself = weakref.ref(self)
def cb(wparent):
o = wself()
self.wparent = weakref.ref(parent, cb)
d = weakref.WeakKeyDictionary()
root = c = C(None)
for n in range(100):
d[c] = c = C(c)
del root
gc.collect()
def test_callback_attribute(self):
x = Object(1)
callback = lambda ref: None
ref1 = weakref.ref(x, callback)
self.assertIs(ref1.__callback__, callback)
ref2 = weakref.ref(x)
self.assertIsNone(ref2.__callback__)
def test_callback_attribute_after_deletion(self):
x = Object(1)
ref = weakref.ref(x, self.callback)
self.assertIsNotNone(ref.__callback__)
del x
support.gc_collect()
self.assertIsNone(ref.__callback__)
def test_set_callback_attribute(self):
x = Object(1)
callback = lambda ref: None
ref1 = weakref.ref(x, callback)
with self.assertRaises(AttributeError):
ref1.__callback__ = lambda ref: None
def test_callback_gcs(self):
class ObjectWithDel(Object):
def __del__(self): pass
x = ObjectWithDel(1)
ref1 = weakref.ref(x, lambda ref: support.gc_collect())
del x
support.gc_collect()
class SubclassableWeakrefTestCase(TestBase):
def test_subclass_refs(self):
class MyRef(weakref.ref):
def __init__(self, ob, callback=None, value=42):
self.value = value
super().__init__(ob, callback)
def __call__(self):
self.called = True
return super().__call__()
o = Object("foo")
mr = MyRef(o, value=24)
self.assertIs(mr(), o)
self.assertTrue(mr.called)
self.assertEqual(mr.value, 24)
del o
gc_collect() # For PyPy or other GCs.
self.assertIsNone(mr())
self.assertTrue(mr.called)
def test_subclass_refs_dont_replace_standard_refs(self):
class MyRef(weakref.ref):
pass
o = Object(42)
r1 = MyRef(o)
r2 = weakref.ref(o)
self.assertIsNot(r1, r2)
self.assertEqual(weakref.getweakrefs(o), [r2, r1])
self.assertEqual(weakref.getweakrefcount(o), 2)
r3 = MyRef(o)