https://github.com/python/cpython/commit/f9132f1c555f0e47d7e38251f96adaf0355f9c08
commit: f9132f1c555f0e47d7e38251f96adaf0355f9c08
branch: main
author: Christian Aurich Zanettini Martins <[email protected]>
committer: methane <[email protected]>
date: 2026-10-13T03:07:34Z
summary:
gh-159285: Fix crash when copying an empty dict fails with MemoryError (#159286)
copy_lock_held_untracked() asserted that the new empty dict was not
tracked by the GC without checking whether its allocation had failed,
so a debug build dereferenced NULL instead of raising MemoryError. This
affected dict.copy(), PyDict_Copy() and _PyDict_CopyAsDict(), which
type() uses for the class namespace.
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-10-12-23-32-50.gh-issue-159285.nlLuwQ.rst
M Lib/test/test_dict.py
M Objects/dictobject.c
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 26bdaa9d6a35b7..9d013e3d2caa1c 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -479,6 +479,13 @@ def test_copy_noncompact(self):
d2 = d.copy()
self.assertEqual(d2, d)
+ @support.nomemtest
+ def test_copy_empty_no_memory(self):
+ import _testcapi
+ d = {}
+ with self.assertRaises(MemoryError):
+ _testcapi.call_with_nomemory(0, 0, d.copy)
+
def test_get(self):
d = {}
self.assertIs(d.get('c'), None)
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-10-12-23-32-50.gh-issue-159285.nlLuwQ.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-12-23-32-50.gh-issue-159285.nlLuwQ.rst
new file mode 100644
index 00000000000000..0cb795f8309f73
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-12-23-32-50.gh-issue-159285.nlLuwQ.rst
@@ -0,0 +1,2 @@
+Fix a crash in a debug build when copying an empty :class:`dict` fails with
+:exc:`MemoryError`. Patch by Christian Aurich Zanettini Martins.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index eed9bd92c55bf2..13c9e2e4b395ab 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -4497,7 +4497,7 @@ copy_lock_held_untracked(PyObject *o, int as_frozendict)
else {
d = dict_new_untracked(&PyDict_Type);
}
- assert(!_PyObject_GC_IS_TRACKED(d));
+ assert(d == NULL || !_PyObject_GC_IS_TRACKED(d));
return d;
}
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