diff options
| -rw-r--r-- | Lib/test/test_long.py | 15 | ||||
| -rw-r--r-- | Misc/NEWS | 3 | ||||
| -rw-r--r-- | Objects/longobject.c | 5 |
3 files changed, 23 insertions, 0 deletions
diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py index f0dd0749f7..4d293f24e0 100644 --- a/Lib/test/test_long.py +++ b/Lib/test/test_long.py @@ -878,6 +878,21 @@ class LongTest(unittest.TestCase): self.check_truediv(-x, y) self.check_truediv(-x, -y) + def test_lshift_of_zero(self): + self.assertEqual(0 << 0, 0) + self.assertEqual(0 << 10, 0) + with self.assertRaises(ValueError): + 0 << -1 + + @support.cpython_only + def test_huge_lshift_of_zero(self): + # Shouldn't try to allocate memory for a huge shift. See issue #27870. + # Other implementations may have a different boundary for overflow, + # or not raise at all. + self.assertEqual(0 << sys.maxsize, 0) + with self.assertRaises(OverflowError): + 0 << (sys.maxsize + 1) + def test_small_ints(self): for i in range(-5, 257): self.assertIs(i, i + 0) @@ -10,6 +10,9 @@ What's New in Python 3.6.0 beta 1 Core and Builtins ----------------- +- Issue #27870: A left shift of zero by a large integer no longer attempts + to allocate large amounts of memory. + - Issue #25402: In int-to-decimal-string conversion, improve the estimate of the intermediate memory required, and remove an unnecessarily strict overflow check. Patch by Serhiy Storchaka. diff --git a/Objects/longobject.c b/Objects/longobject.c index ba23599535..9d6474c6bd 100644 --- a/Objects/longobject.c +++ b/Objects/longobject.c @@ -4281,6 +4281,11 @@ long_lshift(PyObject *v, PyObject *w) PyErr_SetString(PyExc_ValueError, "negative shift count"); return NULL; } + + if (Py_SIZE(a) == 0) { + return PyLong_FromLong(0); + } + /* wordshift, remshift = divmod(shiftby, PyLong_SHIFT) */ wordshift = shiftby / PyLong_SHIFT; remshift = shiftby - wordshift * PyLong_SHIFT; |