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bpo-44523: Remove the pass-through for hash() in weakref proxy objects (GH-26950)

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Pablo Galindo 2021-06-29 23:58:45 +01:00 • committed by GitHub
parent 12803c59d5
commit e2fea101fd
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3 changed files with 15 additions and 20 deletions
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14
Lib/test/test_weakref.py
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@ -422,14 +422,20 @@ class ReferencesTestCase(TestBase):
self.assertEqual("".join(reversed(weakref.proxy(obj))), "cba") self.assertEqual("".join(reversed(weakref.proxy(obj))), "cba")
def test_proxy_hash(self): def test_proxy_hash(self):
cool_hash = 299_792_458
class MyObj: class MyObj:
def __hash__(self): def __hash__(self):
return cool_hash return 42
obj = MyObj() obj = MyObj()
self.assertEqual(hash(weakref.proxy(obj)), cool_hash) 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): def test_getweakrefcount(self):
o = C() o = C()

3
Misc/NEWS.d/next/Core and Builtins/2021-06-29-11-49-29.bpo-44523.67-ZIP.rst Normal file
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@ -0,0 +1,3 @@
Remove the pass-through for :func:`hash` of :class:`weakref.proxy` objects
to prevent unintended consequences when the original referred object
dies while the proxy is part of a hashable object. Patch by Pablo Galindo.

18
Objects/weakrefobject.c
View file

@ -732,21 +732,6 @@ static PyMappingMethods proxy_as_mapping = {
}; };
static Py_hash_t
proxy_hash(PyObject *self)
{
PyWeakReference *proxy = (PyWeakReference *)self;
if (!proxy_checkref(proxy)) {
return -1;
}
PyObject *obj = PyWeakref_GET_OBJECT(proxy);
Py_INCREF(obj);
Py_hash_t res = PyObject_Hash(obj);
Py_DECREF(obj);
return res;
}
PyTypeObject PyTypeObject
_PyWeakref_ProxyType = { _PyWeakref_ProxyType = {
PyVarObject_HEAD_INIT(&PyType_Type, 0) PyVarObject_HEAD_INIT(&PyType_Type, 0)
@ -763,7 +748,8 @@ _PyWeakref_ProxyType = {
&proxy_as_number, /* tp_as_number */ &proxy_as_number, /* tp_as_number */
&proxy_as_sequence, /* tp_as_sequence */ &proxy_as_sequence, /* tp_as_sequence */
&proxy_as_mapping, /* tp_as_mapping */ &proxy_as_mapping, /* tp_as_mapping */
proxy_hash, /* tp_hash */ // Notice that tp_hash is intentionally omitted as proxies are "mutable" (when the reference dies).
0, /* tp_hash */
0, /* tp_call */ 0, /* tp_call */
proxy_str, /* tp_str */ proxy_str, /* tp_str */
proxy_getattr, /* tp_getattro */ proxy_getattr, /* tp_getattro */