From 91e96ab0796e18a05f0a00b6f1ebd348be46cad8 Mon Sep 17 00:00:00 2001
From: Victor Felder <victor@draft.li>
Date: Mon, 2 Jan 2017 22:28:04 +0100
Subject: [PATCH] events: avoid emit() eager deopt

This commit makes sure EventEmitter.emit() doesn't get deoptimized by
V8. The deopt happens when accessing out of bound indexes of the
`arguments` object.

This issue has been raised here: #10323 and this specific case might
become a more serious performance issue in upcoming V8 releases.

PR-URL: https://github.com/nodejs/node/pull/10568
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
---
 lib/events.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/events.js b/lib/events.js
index 209700e65ad596..000fa98d5a88c5 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -148,7 +148,8 @@ EventEmitter.prototype.emit = function emit(type) {
 
   // If there is no 'error' event listener then throw.
   if (doError) {
-    er = arguments[1];
+    if (arguments.length > 1)
+      er = arguments[1];
     if (domain) {
       if (!er)
         er = new Error('Uncaught, unspecified "error" event');