[Python-checkins] bpo-33989: Ensure that ms.key_compare is always initialized in list_sort_impl(). (GH-8710)

[Serhiy Storchaka]

https://github.com/python/cpython/commit/ebc793d6acb9650b9f497808e059805892031d74
commit: ebc793d6acb9650b9f497808e059805892031d74
branch: master
author: Zackery Spytz <zspytz at gmail.com>
committer: Serhiy Storchaka <storchaka at gmail.com>
date: 2019-02-21T09:47:14+02:00
summary:

bpo-33989: Ensure that ms.key_compare is always initialized in list_sort_impl(). (GH-8710)

files:
A Misc/NEWS.d/next/Core and Builtins/2018-08-08-20-52-55.bpo-33989.TkLBui.rst
M Objects/listobject.c

diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-08-08-20-52-55.bpo-33989.TkLBui.rst b/Misc/NEWS.d/next/Core and Builtins/2018-08-08-20-52-55.bpo-33989.TkLBui.rst
new file mode 100644
index 000000000000..056a71c480ad
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-08-08-20-52-55.bpo-33989.TkLBui.rst	
@@ -0,0 +1,2 @@
+Fix a possible crash in :meth:`list.sort` when sorting objects with
+``ob_type->tp_richcompare == NULL``.  Patch by Zackery Spytz.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index a08b3b50dd9a..cbd6e81ea472 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2334,6 +2334,9 @@ list_sort_impl(PyListObject *self, PyObject *keyfunc, int reverse)
             else if ((ms.key_richcompare = key_type->tp_richcompare) != NULL) {
                 ms.key_compare = unsafe_object_compare;
             }
+            else {
+                ms.key_compare = safe_object_compare;
+            }
         }
         else {
             ms.key_compare = safe_object_compare;