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gh-140406: Fix memory leak upon __hash__ returning a non-integer #140411

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Merged
merged 5 commits into from
Oct 21, 2025
Merged

gh-140406: Fix memory leak upon __hash__ returning a non-integer #140411

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b1013fe
Fix memory leak upon __hash__ returning a non-integer.
ZeroIntensity Oct 21, 2025
ed017f0
Add a test case.
ZeroIntensity Oct 21, 2025
9f89372
Add blurb.
ZeroIntensity Oct 21, 2025
1b96db7
Remove unnecessary loop.
ZeroIntensity Oct 21, 2025
5754822
Move test to test_builtin.
ZeroIntensity Oct 21, 2025
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11 changes: 11 additions & 0 deletions Lib/test/test_hash.py
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Original file line number Diff line number Diff line change
Expand Up @@ -166,6 +166,17 @@ def test_hashes(self):
for obj in self.hashes_to_check:
self.assertEqual(hash(obj), _default_hash(obj))

def test_invalid_hash_typeerror(self):
# GH-140406: The returned object from __hash__() would leak if it
# wasn't an integer.
class A:
def __hash__(self):
return 1.0

for _ in range(100):
with self.assertRaises(TypeError):
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The ref leak checker should catch it even in one iteration, is 100 needed here?

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It's a very tiny leak, so I wasn't sure if it would be caught. I don't mind removing it.

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Done.

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test_hash in test_builtin is also a good place. It already contains similar tests (TypeErrors and classes with custom __hash__).

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Good idea, I moved it to test_builtin.

hash(A())

class HashRandomizationTests:

# Each subclass should define a field "repr_", containing the repr() of
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-10-21-06-51-50.gh-issue-140406.0gJs8M.rst
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@@ -0,0 +1,2 @@
Fix memory leak when an object's :meth:`~object.__hash__` method returns an
object that isn't an :class:`int`.
1 change: 1 addition & 0 deletions Objects/typeobject.c
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Expand Up @@ -10569,6 +10569,7 @@ slot_tp_hash(PyObject *self)
return PyObject_HashNotImplemented(self);
}
if (!PyLong_Check(res)) {
Py_DECREF(res);
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I suggest to move this line below PyErr_SetString(). Later, it can be used to format a better error message.

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I think we should do that in a different PR, where we change the error message. I generally like to call Py_DECREF before PyErr* functions to protect against badly crafted destructors that break the exception state. But, if you feel strongly about this, I'm also fine with moving it.

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I do not feel strongly about this. It would just make the future diff a little bit smaller, and git blame would show your commit instead of the following commit.
In general, I prefer to call Py_DECREF before PyErr* functions too.

PyErr_SetString(PyExc_TypeError,
"__hash__ method should return an integer");
return -1;
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