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gh-152228: Fix a crash in str.replace under a limited memory case #152229

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gh-152228: Fix a crash in str.replace under a limited memory case #152229

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gh-152228: Fix a crash in `str.replace` under a limited memory case
sobolevn Jun 25, 2026
07f2ff4
Update Lib/test/test_str.py
sobolevn Jun 25, 2026
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17 changes: 17 additions & 0 deletions Lib/test/test_str.py
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Original file line number Diff line number Diff line change
Expand Up @@ -607,6 +607,23 @@ def test_replace_id(self):
text = 'abc def'
self.assertIs(text.replace(pattern, pattern), text)

@support.cpython_only
@unittest.skipIf(_testcapi is None, reason="_testcapi is required for this test")
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@unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
def test_replace_oom(self):
# https://github.com/python/cpython/issues/152228
s1 = "轘" * 4
s2 = "&"
s3 = "&"
assertion = self.assertRaises(MemoryError)
_testcapi.set_nomemory(0, 0)
try:
# No allocations made in the test itself:
with assertion:
s1.replace(s2, s3) # this line used to crash before
finally:
_testcapi.remove_mem_hooks()

def test_repeat_id_preserving(self):
a = '123abc1@'
b = '456zyx-+'
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-06-25-21-34-15.gh-issue-152228.a6K14K.rst
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@@ -0,0 +1 @@
Fix a crash in :meth:`str.replace` under a limited memory situation.
18 changes: 9 additions & 9 deletions Objects/unicodeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -10753,9 +10753,9 @@ replace(PyObject *self, PyObject *str1,
}

done:
assert(srelease == (sbuf != PyUnicode_DATA(self)));
assert(release1 == (buf1 != PyUnicode_DATA(str1)));
assert(release2 == (buf2 != PyUnicode_DATA(str2)));
assert(srelease == (sbuf != NULL && sbuf != PyUnicode_DATA(self)));
assert(release1 == (buf1 != NULL && buf1 != PyUnicode_DATA(str1)));
assert(release2 == (buf2 != NULL && buf2 != PyUnicode_DATA(str2)));
if (srelease)
PyMem_Free((void *)sbuf);
if (release1)
Expand All @@ -10767,9 +10767,9 @@ replace(PyObject *self, PyObject *str1,

nothing:
/* nothing to replace; return original string (when possible) */
assert(srelease == (sbuf != PyUnicode_DATA(self)));
assert(release1 == (buf1 != PyUnicode_DATA(str1)));
assert(release2 == (buf2 != PyUnicode_DATA(str2)));
assert(srelease == (sbuf != NULL && sbuf != PyUnicode_DATA(self)));
assert(release1 == (buf1 != NULL && buf1 != PyUnicode_DATA(str1)));
assert(release2 == (buf2 != NULL && buf2 != PyUnicode_DATA(str2)));
if (srelease)
PyMem_Free((void *)sbuf);
if (release1)
Expand All @@ -10779,9 +10779,9 @@ replace(PyObject *self, PyObject *str1,
return unicode_result_unchanged(self);

error:
assert(srelease == (sbuf != PyUnicode_DATA(self)));
assert(release1 == (buf1 != PyUnicode_DATA(str1)));
assert(release2 == (buf2 != PyUnicode_DATA(str2)));
assert(srelease == (sbuf != NULL && sbuf != PyUnicode_DATA(self)));
assert(release1 == (buf1 != NULL && buf1 != PyUnicode_DATA(str1)));
assert(release2 == (buf2 != NULL && buf2 != PyUnicode_DATA(str2)));
if (srelease)
PyMem_Free((void *)sbuf);
if (release1)
Expand Down
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