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gh-152107: Fix crash when creating a dict item iterator under MemoryError #152110

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gh-152107: Fix crash when creating a dict item iterator under MemoryError #152110

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c41df03
Address Review Comments
zangjiucheng Jun 24, 2026
2886cb8
Fix formatting of comment in dictiter_new function
zangjiucheng Jun 24, 2026
309c9a7
Fix crash in dict item iterator creation under memory-allocation failure
zangjiucheng Jun 24, 2026
a6cf8a4
Merge branch 'main' into gh-152107
zangjiucheng Jun 25, 2026
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20 changes: 20 additions & 0 deletions Lib/test/test_dict.py
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,26 @@ def test_items(self):
self.assertRaises(TypeError, d.items, None)
self.assertEqual(repr(dict(a=1).items()), "dict_items([('a', 1)])")

@support.cpython_only
def test_item_iterator_oom(self):
import_helper.import_module('_testcapi')
from test.support.script_helper import assert_python_ok
code = """if 1:
import _testcapi
items = {1: 2, 3: 4}.items()
ballast = [(i, i) for i in range(3000)]
held = []
for start in range(1, 5):
_testcapi.set_nomemory(start)
try:
held.append(iter(items))
except MemoryError:
pass
finally:
_testcapi.remove_mem_hooks()
"""
assert_python_ok('-c', code)

def test_views_mapping(self):
mappingproxy = type(type.__dict__)
class Dict(dict):
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-06-24-14-05-00.gh-issue-152107.K3jX9p.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a crash when creating a :class:`dict` item iterator (for example
``iter(d.items())`` or ``reversed(d.items())``) under a memory-allocation
failure. Patch by Jiucheng Zang.
9 changes: 5 additions & 4 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5507,6 +5507,7 @@ dictiter_new(PyDictObject *dict, PyTypeObject *itertype)
used = GET_USED(dict);
di->di_used = used;
di->len = used;
di->di_result = NULL;
if (itertype == &PyDictRevIterKey_Type ||
itertype == &PyDictRevIterItem_Type ||
itertype == &PyDictRevIterValue_Type) {
Expand All @@ -5520,6 +5521,10 @@ dictiter_new(PyDictObject *dict, PyTypeObject *itertype)
else {
di->di_pos = 0;
}
/* gh-152107: track before allocating di_result. A dictiter with a NULL
di_result is a valid state for dictiter_traverse()/dictiter_dealloc(),
so a failure of the allocation below can safely DECREF a tracked di. */
_PyObject_GC_TRACK(di);
if (itertype == &PyDictIterItem_Type ||
itertype == &PyDictRevIterItem_Type) {
di->di_result = _PyTuple_FromPairSteal(Py_None, Py_None);
Expand All @@ -5528,10 +5533,6 @@ dictiter_new(PyDictObject *dict, PyTypeObject *itertype)
return NULL;
}
}
else {
di->di_result = NULL;
}
_PyObject_GC_TRACK(di);
return (PyObject *)di;
}

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