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: #10568 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Evan Lucas <[email protected]> Reviewed-By: Jeremiah Senkpiel <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]>
nodejs · Jan 5, 2017 · e52fee5 · e52fee5
1 parent 26b8c21
commit e52fee5
Showing 1 changed file with 2 additions and 1 deletion.
diff --git 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');