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gh-113841: fix possible undefined division by 0 in _Py_c_pow() (GH-127211)

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`x**y == 1/x**-y ` thus changing `/=` to `*=` by negating the exponent.
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Sergey B Kirpichev 2024-11-24 10:37:37 +03:00 • committed by GitHub
parent a4d4c1ede2
commit f7bb658124
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3 changed files with 8 additions and 1 deletions
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5
Lib/test/test_complex.py
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@ -338,6 +338,11 @@ class ComplexTest(ComplexesAreIdenticalMixin, unittest.TestCase):
except OverflowError: except OverflowError:
pass pass
# gh-113841: possible undefined division by 0 in _Py_c_pow()
x, y = 9j, 33j**3
with self.assertRaises(OverflowError):
x**y
def test_pow_with_small_integer_exponents(self): def test_pow_with_small_integer_exponents(self):
# Check that small integer exponents are handled identically # Check that small integer exponents are handled identically
# regardless of their type. # regardless of their type.

2
Misc/NEWS.d/next/Core_and_Builtins/2024-11-24-07-01-28.gh-issue-113841.WFg-Bu.rst Normal file
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@ -0,0 +1,2 @@
Fix possible undefined behavior division by zero in :class:`complex`'s
:c:func:`_Py_c_pow`.

2
Objects/complexobject.c
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@ -168,7 +168,7 @@ _Py_c_pow(Py_complex a, Py_complex b)
at = atan2(a.imag, a.real); at = atan2(a.imag, a.real);
phase = at*b.real; phase = at*b.real;
if (b.imag != 0.0) { if (b.imag != 0.0) {
len /= exp(at*b.imag); len *= exp(-at*b.imag);
phase += b.imag*log(vabs); phase += b.imag*log(vabs);
} }
r.real = len*cos(phase); r.real = len*cos(phase);