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gh-142554: avoid divmod crashes due to bad _pylong.int_divmod (#142673)

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Bénédikt Tran 2025-12-14 09:38:23 +01:00 • committed by GitHub
parent 39ecb17103
commit 4e4163676a
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3 changed files with 16 additions and 2 deletions
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12
Lib/test/test_int.py
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@ -778,6 +778,18 @@ def test_pylong_int_divmod(self):
a, b = divmod(n*3 + 1, n)
assert a == 3 and b == 1
@support.cpython_only # tests implementation details of CPython.
@unittest.skipUnless(_pylong, "_pylong module required")
def test_pylong_int_divmod_crash(self):
# Regression test for https://github.com/python/cpython/issues/142554.
bad_int_divmod = lambda a, b: (1,)
# 'k' chosen such that divmod(2**(2*k), 2**k) uses _pylong.int_divmod()
k = 10_000
a, b = (1 << (2 * k)), (1 << k)
with mock.patch.object(_pylong, "int_divmod", wraps=bad_int_divmod):
msg = r"tuple of length 2 is required from int_divmod\(\)"
self.assertRaisesRegex(ValueError, msg, divmod, a, b)
def test_pylong_str_to_int(self):
v1 = 1 << 100_000
s = str(v1)

2
Misc/NEWS.d/next/Core_and_Builtins/2025-12-13-17-20-38.gh-issue-142554.wNtEFF.rst Normal file
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@ -0,0 +1,2 @@
Fix a crash in :func:`divmod` when :func:`!_pylong.int_divmod` does not
return a tuple of length two exactly. Patch by Bénédikt Tran.

4
Objects/longobject.c
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@ -4434,10 +4434,10 @@ pylong_int_divmod(PyLongObject *v, PyLongObject *w,
if (result == NULL) {
return -1;
}
if (!PyTuple_Check(result)) {
if (!PyTuple_Check(result) || PyTuple_GET_SIZE(result) != 2) {
Py_DECREF(result);
PyErr_SetString(PyExc_ValueError,
"tuple is required from int_divmod()");
"tuple of length 2 is required from int_divmod()");
return -1;
}
PyObject *q = PyTuple_GET_ITEM(result, 0);