https://github.com/python/cpython/commit/a9a91d06a0e1faad9a56d4e652e4a7a98033adf8 commit: a9a91d06a0e1faad9a56d4e652e4a7a98033adf8 branch: 3.14 author: Serhiy Storchaka <[email protected]> committer: serhiy-storchaka <[email protected]> date: 2026-07-06T18:46:04Z summary:
[3.14] gh-153200: Fix math.isqrt() for int subclasses with overridden comparison operators (GH-153203) (GH-153225) The final check-and-correct comparison in the arbitrary precision path could call a comparison operator overridden in an int subclass. Compare by value with int's tp_richcompare. (cherry picked from commit 3a1b5473f217fc493f743c9ca8b877d2e76f8e6b) Co-authored-by: Claude Fable 5 <[email protected]> files: A Misc/NEWS.d/next/Library/2026-07-06-12-00-00.gh-issue-153200.isqrtLt.rst M Lib/test/test_math.py M Modules/mathmodule.c diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py index 5f64df60c92a3f..fd7d1a1c61cfd7 100644 --- a/Lib/test/test_math.py +++ b/Lib/test/test_math.py @@ -238,6 +238,19 @@ def __init__(self, value): def __index__(self): return self.value +# int subclass with broken arithmetic operators; implementations must +# convert their arguments to exact ints instead of using these. +class BadIntSubclass(int): + def _binop(self, other='ignored', mod=None): + return 42 + __add__ = __radd__ = __sub__ = __rsub__ = _binop + __mul__ = __rmul__ = __mod__ = __rmod__ = _binop + __divmod__ = __rdivmod__ = __pow__ = __rpow__ = _binop + __floordiv__ = __rfloordiv__ = _binop + __lshift__ = __rlshift__ = __rshift__ = __rrshift__ = _binop + __and__ = __rand__ = __or__ = __ror__ = __xor__ = __rxor__ = _binop + __lt__ = __le__ = __gt__ = __ge__ = _binop + class BadDescr: def __get__(self, obj, objtype=None): raise ValueError @@ -1117,6 +1130,16 @@ def __index__(self): self.assertIs(type(s), int) self.assertEqual(s, 41) + # Overridden operators of an int subclass must not affect the + # result. + s = math.isqrt(BadIntSubclass(10**20)) + self.assertIs(type(s), int) + self.assertEqual(s, 10**10) + + s = math.isqrt(BadIntSubclass(10**20 - 1)) + self.assertIs(type(s), int) + self.assertEqual(s, 10**10 - 1) + with self.assertRaises(ValueError): math.isqrt(IntegerLike(-3)) diff --git a/Misc/NEWS.d/next/Library/2026-07-06-12-00-00.gh-issue-153200.isqrtLt.rst b/Misc/NEWS.d/next/Library/2026-07-06-12-00-00.gh-issue-153200.isqrtLt.rst new file mode 100644 index 00000000000000..a27ac73fe31a70 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-07-06-12-00-00.gh-issue-153200.isqrtLt.rst @@ -0,0 +1,3 @@ +Fix :func:`math.isqrt` returning an incorrect result for arguments not +less than 2**64 that are instances of an :class:`int` subclass with an +overridden comparison operator. diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c index b28bfb4ce53efc..51efd38892ca88 100644 --- a/Modules/mathmodule.c +++ b/Modules/mathmodule.c @@ -1793,16 +1793,20 @@ math_isqrt(PyObject *module, PyObject *n) /* The correct result is either a or a - 1. Figure out which, and decrement a if necessary. */ - /* a_too_large = n < a * a */ + /* a_too_large = n < a * a. Compare by value: n can be an instance + of an int subclass with an overridden __lt__ method. */ b = PyNumber_Multiply(a, a); if (b == NULL) { goto error; } - a_too_large = PyObject_RichCompareBool(n, b, Py_LT); + PyObject *cmp = PyLong_Type.tp_richcompare(n, b, Py_LT); Py_DECREF(b); - if (a_too_large == -1) { + if (cmp == NULL) { goto error; } + assert(PyBool_Check(cmp)); + a_too_large = (cmp == Py_True); + Py_DECREF(cmp); if (a_too_large) { Py_SETREF(a, PyNumber_Subtract(a, _PyLong_GetOne())); _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
