pythoncapi
diff --git a/‎Misc/NEWS.d/next/Core and Builtins/2017-09-04-16-35-06.bpo-31347.KDuf2w.rst‎
Lines changed: 1 addition & 0 deletions b/‎Misc/NEWS.d/next/Core and Builtins/2017-09-04-16-35-06.bpo-31347.KDuf2w.rst‎
Lines changed: 1 addition & 0 deletions
diff --git a/‎Objects/call.c‎
Lines changed: 3 additions & 3 deletions b/‎Objects/call.c‎
Lines changed: 3 additions & 3 deletions
@@ -0,0 +1 @@
+Fix possible undefined behavior in _PyObject_FastCall_Prepend.
@@ -854,9 +854,9 @@ _PyObject_FastCall_Prepend(PyObject *callable,
 
     /* use borrowed references */
     args2[0] = obj;
-    memcpy(&args2[1],
-           args,
-           (nargs - 1)* sizeof(PyObject *));
+    if (nargs > 1) {
+        memcpy(&args2[1], args, (nargs - 1) * sizeof(PyObject *));
+    }
 
     result = _PyObject_FastCall(callable, args2, nargs);
     if (args2 != small_stack) {
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Fix possible undefined behavior in _PyObject_FastCall_Prepend.`