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

(cherry picked from commit ebc793d6acb9650b9f497808e059805892031d74)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

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 (file)
index 0000000..056a71c
--- /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 de73b8bf80fdfd01848425e9e466229ef6a53f96..7dc68a73bdb626bc870db614b7d3d65753533f89 100644 (file)
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2279,6 +2279,9 @@ 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;