diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_5/extensions/regress-313938.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_5/extensions/regress-313938.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,54 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 313938;
+var summary = 'Root access in jsscript.c';
+var actual = '';
+var expect = '';
+
+printBugNumber(BUGNUMBER);
+printStatus (summary);
+
+if (typeof Script == 'undefined')
+{
+  print('Test skipped. Script not defined.');
+  reportCompare("Script not defined, Test skipped.",
+                "Script not defined, Test skipped.",
+                summary);
+}
+else
+{
+  var str = " 2;".substring(1);
+  "1".substring(2);
+  expect = Script.prototype.compile(str).toSource();
+
+  var likeString = {
+    toString: function() {
+      var tmp = str;
+      str = null;
+      return tmp;
+    }
+  };
+
+  TWO = 2.0;
+
+  var likeObject = {
+    valueOf: function() {
+      if (typeof gc == "function")
+        gc();
+      for (var i = 0; i != 40000; ++i) {
+        var tmp = 1e100 * TWO;
+      }
+      return this;
+    }
+  }
+
+  var s = Script.prototype.compile(likeString, likeObject);
+  var actual = s.toSource();
+  printStatus(expect === actual);
+
+  reportCompare(expect, actual, summary);
+}