Abort from calling `OrderedDict.setdefault` with an invalid value

[devdanzin]

Crash report

What happened?

It's possible to abort the interpreter by passing a class that has invalid, changing hash values to OrderedDict.setdefault:

from abc import ABCMeta
from random import randint

large_num = 2**64
class WeirdBase(ABCMeta):
  def __hash__(self):
    return randint(0, large_num)


class weird_bytes(bytes, metaclass=WeirdBase):
    pass

from collections import OrderedDict

obj = OrderedDict()

for x in range(100):
    obj.setdefault(weird_bytes, None)

Abort message:

python: Objects/odictobject.c:1036: OrderedDict_setdefault_impl: Assertion `_odict_find_node(self, key) == NULL' failed.

Program received signal SIGABRT, Aborted.

Found using fusil by @vstinner.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

Python 3.14.0a6+ (heads/main:be2d2181e62, Mar 31 2025, 07:30:17) [GCC 11.4.0]

Linked PRs

• gh-132461: Fix crash in OrderedDict.setdefault when key has unstable hash #132462

[lemorage]

Can unstable hashes be a key in a dict?

[dura0ok]

@lemorage yeah, i think no. We should check it and give normal error to user.