From 91f0d4aa2fae249479e5ecdc76aee6f5c13d0994 Mon Sep 17 00:00:00 2001
From: Victor Stinner <victor.stinner@gmail.com>
Date: Thu, 19 Jan 2017 12:45:06 +0100
Subject: Add a note explaining why dict_update() doesn't use METH_FASTCALL

Issue #29312.
---
 Objects/dictobject.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 1a6eedd..f941486 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -2347,6 +2347,9 @@ dict_update_common(PyObject *self, PyObject *args, PyObject *kwds,
     return result;
 }
 
+/* Note: dict.update() uses the METH_VARARGS|METH_KEYWORDS calling convention.
+   Using METH_FASTCALL would make dict.update(**dict2) calls slower, see the
+   issue #29312. */
 static PyObject *
 dict_update(PyObject *self, PyObject *args, PyObject *kwds)
 {
-- 
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