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gh-152017: Fix deque_clear to no longer alters exceptions #152018

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gh-152017: Fix deque_clear to no longer alters exceptions #152018

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gh-152017: Fix `deque_clear` to no longer alters exceptions
brijkapadia Jun 23, 2026
40dd821
📜🤖 Added by blurb_it.
blurb-it[bot] Jun 23, 2026
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17 changes: 17 additions & 0 deletions Lib/test/test_collections.py
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
from test.support.import_helper import import_fresh_module
import types
import unittest
import _testcapi

from collections import namedtuple, Counter, OrderedDict, _count_elements
from collections import UserDict, UserString, UserList
Expand Down Expand Up @@ -2475,6 +2476,22 @@ def test_symmetric_difference(self):
pp ^= qq
self.assertEqual(pp, r)

################################################################################
### Deque
################################################################################

class TestDeque(unittest.TestCase):

def test_deque_oom(self):
for n in range(1, 80):
d = deque(range(200))
_testcapi.set_nomemory(n, 0)

@StanFromIreland StanFromIreland Jun 23, 2026

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These tests are too troublesome so we generally avoid them (e.g., _testcapi is not always available or when Py_TRACE_REFS is set it conflicts).

try:
d.copy()
_testcapi.remove_mem_hooks()
break
except MemoryError:
_testcapi.remove_mem_hooks()

def load_tests(loader, tests, pattern):
tests.addTest(doctest.DocTestSuite(collections))
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2026-06-23-15-02-27.gh-issue-152017.wH89hr.rst
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@@ -0,0 +1 @@
:class:`collections.deque` no longer suppresses :exc:`MemoryError` in certain cases.
3 changes: 2 additions & 1 deletion Modules/_collectionsmodule.c
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Expand Up @@ -746,9 +746,10 @@ deque_clear(PyObject *self)
adversary could cause it to never terminate).
*/

PyObject *old_exc = PyErr_GetRaisedException();
b = newblock(deque);
PyErr_SetRaisedException(old_exc);
if (b == NULL) {
PyErr_Clear();
goto alternate_method;
}

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