From 5a7d923e7561d6e2bd8ad505178efa2d27ebd785 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Tue, 6 Sep 2016 17:58:25 -0700
Subject: [PATCH] make sure to not call memcpy with a NULL second argument

---
 Objects/listobject.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Objects/listobject.c b/Objects/listobject.c
index d688179d6b4..815a1b9ea2d 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -634,14 +634,17 @@ list_ass_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
     item = a->ob_item;
     /* recycle the items that we are about to remove */
     s = norig * sizeof(PyObject *);
-    if (s > sizeof(recycle_on_stack)) {
-        recycle = (PyObject **)PyMem_MALLOC(s);
-        if (recycle == NULL) {
-            PyErr_NoMemory();
-            goto Error;
+    /* If norig == 0, item might be NULL, in which case we may not memcpy from it. */
+    if (s) {
+        if (s > sizeof(recycle_on_stack)) {
+            recycle = (PyObject **)PyMem_MALLOC(s);
+            if (recycle == NULL) {
+                PyErr_NoMemory();
+                goto Error;
+            }
         }
+        memcpy(recycle, &item[ilow], s);
     }
-    memcpy(recycle, &item[ilow], s);
 
     if (d < 0) { /* Delete -d items */
         Py_ssize_t tail;