From c139f145b1be904d7c3e1d01f4be3c123b04b9b3 Mon Sep 17 00:00:00 2001
From: Sergey B Kirpichev <skirpichev@gmail.com>
Date: Tue, 28 Apr 2015 23:01:12 +0300
Subject: [PATCH] list.sort(): Add quick exit if length of list <= 1

---
 Lib/test/test_sort.py | 14 ++++++++++++++
 Objects/listobject.c  |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/Lib/test/test_sort.py b/Lib/test/test_sort.py
index a5d0ebf..8c31868 100644
--- a/Lib/test/test_sort.py
+++ b/Lib/test/test_sort.py
@@ -166,6 +166,20 @@ class TestBugs(unittest.TestCase):
             self.assertRaises(ValueError, L.sort, key=cmp_to_key(mutating_cmp))
             memorywaster = [memorywaster]
 
+    def test_bug24075(self):
+        # sort() should do quick exit if len(list) <= 1
+
+        L = [1]
+        def spam(x):
+            raise Exception
+        try:
+            L.sort(key=spam)
+            raised = False
+        except Exception:
+            raised = True
+
+        self.assertFalse(raised)
+
 #==============================================================================
 
 class TestDecorateSortUndecorate(unittest.TestCase):
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 45e54ce..6741826 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -1938,6 +1938,9 @@ listsort(PyListObject *self, PyObject *args, PyObject *kwds)
     if (keyfunc == Py_None)
         keyfunc = NULL;
 
+    if (Py_SIZE(self) <= 1)
+        Py_RETURN_NONE;
+
     /* The list is temporarily made empty, so that mutations performed
      * by comparison functions can't affect the slice of memory we're
      * sorting (allowing mutations during sorting is a core-dump
-- 
1.9.1