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Rework integer overflow path in math.prod and add more tests (GH-11809)

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The overflow check was relying on undefined behaviour as it was using the result of the multiplication to do the check, and once the overflow has already happened, any operation on the result is undefined behaviour.

Some extra checks that exercise code paths related to this are also added.
This commit is contained in:
Pablo Galindo 2019-03-09 19:18:08 +00:00 • committed by GitHub
parent 62fa51f121
commit 0411411c6b
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2 changed files with 137 additions and 40 deletions
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121
Lib/test/test_math.py
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@ -1595,6 +1595,92 @@ class MathTests(unittest.TestCase):
self.fail('Failures in test_mtestfile:\n ' +
'\n '.join(failures))
def test_prod(self):
prod = math.prod
self.assertEqual(prod([]), 1)
self.assertEqual(prod([], start=5), 5)
self.assertEqual(prod(list(range(2,8))), 5040)
self.assertEqual(prod(iter(list(range(2,8)))), 5040)
self.assertEqual(prod(range(1, 10), start=10), 3628800)
self.assertEqual(prod([1, 2, 3, 4, 5]), 120)
self.assertEqual(prod([1.0, 2.0, 3.0, 4.0, 5.0]), 120.0)
self.assertEqual(prod([1, 2, 3, 4.0, 5.0]), 120.0)
self.assertEqual(prod([1.0, 2.0, 3.0, 4, 5]), 120.0)
# Test overflow in fast-path for integers
self.assertEqual(prod([1, 1, 2**32, 1, 1]), 2**32)
# Test overflow in fast-path for floats
self.assertEqual(prod([1.0, 1.0, 2**32, 1, 1]), float(2**32))
self.assertRaises(TypeError, prod)
self.assertRaises(TypeError, prod, 42)
self.assertRaises(TypeError, prod, ['a', 'b', 'c'])
self.assertRaises(TypeError, prod, ['a', 'b', 'c'], '')
self.assertRaises(TypeError, prod, [b'a', b'c'], b'')
values = [bytearray(b'a'), bytearray(b'b')]
self.assertRaises(TypeError, prod, values, bytearray(b''))
self.assertRaises(TypeError, prod, [[1], [2], [3]])
self.assertRaises(TypeError, prod, [{2:3}])
self.assertRaises(TypeError, prod, [{2:3}]*2, {2:3})
self.assertRaises(TypeError, prod, [[1], [2], [3]], [])
with self.assertRaises(TypeError):
prod([10, 20], [30, 40]) # start is a keyword-only argument
self.assertEqual(prod([0, 1, 2, 3]), 0)
self.assertEqual(prod([1, 0, 2, 3]), 0)
self.assertEqual(prod([1, 2, 3, 0]), 0)
def _naive_prod(iterable, start=1):
for elem in iterable:
start *= elem
return start
# Big integers
iterable = range(1, 10000)
self.assertEqual(prod(iterable), _naive_prod(iterable))
iterable = range(-10000, -1)
self.assertEqual(prod(iterable), _naive_prod(iterable))
iterable = range(-1000, 1000)
self.assertEqual(prod(iterable), 0)
# Big floats
iterable = [float(x) for x in range(1, 1000)]
self.assertEqual(prod(iterable), _naive_prod(iterable))
iterable = [float(x) for x in range(-1000, -1)]
self.assertEqual(prod(iterable), _naive_prod(iterable))
iterable = [float(x) for x in range(-1000, 1000)]
self.assertIsNaN(prod(iterable))
# Float tests
self.assertIsNaN(prod([1, 2, 3, float("nan"), 2, 3]))
self.assertIsNaN(prod([1, 0, float("nan"), 2, 3]))
self.assertIsNaN(prod([1, float("nan"), 0, 3]))
self.assertIsNaN(prod([1, float("inf"), float("nan"),3]))
self.assertIsNaN(prod([1, float("-inf"), float("nan"),3]))
self.assertIsNaN(prod([1, float("nan"), float("inf"),3]))
self.assertIsNaN(prod([1, float("nan"), float("-inf"),3]))
self.assertEqual(prod([1, 2, 3, float('inf'),-3,4]), float('-inf'))
self.assertEqual(prod([1, 2, 3, float('-inf'),-3,4]), float('inf'))
self.assertIsNaN(prod([1,2,0,float('inf'), -3, 4]))
self.assertIsNaN(prod([1,2,0,float('-inf'), -3, 4]))
self.assertIsNaN(prod([1, 2, 3, float('inf'), -3, 0, 3]))
self.assertIsNaN(prod([1, 2, 3, float('-inf'), -3, 0, 2]))
# Type preservation
self.assertEqual(type(prod([1, 2, 3, 4, 5, 6])), int)
self.assertEqual(type(prod([1, 2.0, 3, 4, 5, 6])), float)
self.assertEqual(type(prod(range(1, 10000))), int)
self.assertEqual(type(prod(range(1, 10000), start=1.0)), float)
self.assertEqual(type(prod([1, decimal.Decimal(2.0), 3, 4, 5, 6])),
decimal.Decimal)
# Custom assertions.
def assertIsNaN(self, value):
@ -1724,41 +1810,6 @@ class IsCloseTests(unittest.TestCase):
self.assertAllClose(fraction_examples, rel_tol=1e-8)
self.assertAllNotClose(fraction_examples, rel_tol=1e-9)
def test_prod(self):
prod = math.prod
self.assertEqual(prod([]), 1)
self.assertEqual(prod([], start=5), 5)
self.assertEqual(prod(list(range(2,8))), 5040)
self.assertEqual(prod(iter(list(range(2,8)))), 5040)
self.assertEqual(prod(range(1, 10), start=10), 3628800)
self.assertEqual(prod([1, 2, 3, 4, 5]), 120)
self.assertEqual(prod([1.0, 2.0, 3.0, 4.0, 5.0]), 120.0)
self.assertEqual(prod([1, 2, 3, 4.0, 5.0]), 120.0)
self.assertEqual(prod([1.0, 2.0, 3.0, 4, 5]), 120.0)
# Test overflow in fast-path for integers
self.assertEqual(prod([1, 1, 2**32, 1, 1]), 2**32)
# Test overflow in fast-path for floats
self.assertEqual(prod([1.0, 1.0, 2**32, 1, 1]), float(2**32))
self.assertRaises(TypeError, prod)
self.assertRaises(TypeError, prod, 42)
self.assertRaises(TypeError, prod, ['a', 'b', 'c'])
self.assertRaises(TypeError, prod, ['a', 'b', 'c'], '')
self.assertRaises(TypeError, prod, [b'a', b'c'], b'')
values = [bytearray(b'a'), bytearray(b'b')]
self.assertRaises(TypeError, prod, values, bytearray(b''))
self.assertRaises(TypeError, prod, [[1], [2], [3]])
self.assertRaises(TypeError, prod, [{2:3}])
self.assertRaises(TypeError, prod, [{2:3}]*2, {2:3})
self.assertRaises(TypeError, prod, [[1], [2], [3]], [])
with self.assertRaises(TypeError):
prod([10, 20], [30, 40]) # start is a keyword-only argument
self.assertEqual(prod([0, 1, 2, 3]), 0)
self.assertEqual(prod([1, 0, 2, 3]), 0)
self.assertEqual(prod(range(10)), 0)
def test_main():
from doctest import DocFileSuite