Issue 13496: Fix bisect.bisect overflow bug for large collections.
diff --git a/Lib/test/test_bisect.py b/Lib/test/test_bisect.py
index 93b8613..c24a1a2 100644
--- a/Lib/test/test_bisect.py
+++ b/Lib/test/test_bisect.py
@@ -122,6 +122,13 @@
self.assertRaises(ValueError, mod.insort_left, [1, 2, 3], 5, -1, 3),
self.assertRaises(ValueError, mod.insort_right, [1, 2, 3], 5, -1, 3),
+ def test_large_range(self):
+ # Issue 13496
+ mod = self.module
+ data = range(sys.maxsize-1)
+ self.assertEqual(mod.bisect_left(data, sys.maxsize-3), sys.maxsize-3)
+ self.assertEqual(mod.bisect_right(data, sys.maxsize-3), sys.maxsize-2)
+
def test_random(self, n=25):
from random import randrange
for i in range(n):
diff --git a/Misc/NEWS b/Misc/NEWS
index b045742..91b0c65 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -43,6 +43,9 @@
Library
-------
+- Issue #13496: Fix potential overflow in bisect.bisect algorithm when applied
+ to a collection of size > sys.maxsize / 2.
+
- Issue #14399: zipfile now recognizes that the archive has been modified even
if only the comment is changed. In addition, the TypeError that results from
trying to set a non-binary value as a comment is now now raised at the time
diff --git a/Modules/_bisectmodule.c b/Modules/_bisectmodule.c
index 7fecfc6..93d0eed 100644
--- a/Modules/_bisectmodule.c
+++ b/Modules/_bisectmodule.c
@@ -21,7 +21,10 @@
return -1;
}
while (lo < hi) {
- mid = (lo + hi) / 2;
+ /* The (size_t)cast ensures that the addition and subsequent division
+ are performed as unsigned operations, avoiding difficulties from
+ signed overflow. (See issue 13496.) */
+ mid = ((size_t)lo + hi) / 2;
litem = PySequence_GetItem(list, mid);
if (litem == NULL)
return -1;
@@ -121,7 +124,10 @@
return -1;
}
while (lo < hi) {
- mid = (lo + hi) / 2;
+ /* The (size_t)cast ensures that the addition and subsequent division
+ are performed as unsigned operations, avoiding difficulties from
+ signed overflow. (See issue 13496.) */
+ mid = ((size_t)lo + hi) / 2;
litem = PySequence_GetItem(list, mid);
if (litem == NULL)
return -1;