diff -r 000000000000 -r 6474c204b198 js/src/jsapi-tests/testTrap.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jsapi-tests/testTrap.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,86 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* 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/. */
+
+#include "js/OldDebugAPI.h"
+#include "jsapi-tests/tests.h"
+
+static int emptyTrapCallCount = 0;
+
+static JSTrapStatus
+EmptyTrapHandler(JSContext *cx, JSScript *script, jsbytecode *pc, jsval *rval,
+                 jsval closureArg)
+{
+    JS::RootedValue closure(cx, closureArg);
+    JS_GC(JS_GetRuntime(cx));
+    if (JSVAL_IS_STRING(closure))
+        ++emptyTrapCallCount;
+    return JSTRAP_CONTINUE;
+}
+
+BEGIN_TEST(testTrap_gc)
+{
+    static const char source[] =
+"var i = 0;\n"
+"var sum = 0;\n"
+"while (i < 10) {\n"
+"    sum += i;\n"
+"    ++i;\n"
+"}\n"
+"({ result: sum });\n"
+        ;
+
+    // compile
+    JS::CompileOptions options(cx);
+    options.setFileAndLine(__FILE__, 1);
+    JS::RootedScript script(cx, JS_CompileScript(cx, global, source,
+                                                 strlen(source), options));
+    CHECK(script);
+
+    // execute
+    JS::RootedValue v2(cx);
+    CHECK(JS_ExecuteScript(cx, global, script, &v2));
+    CHECK(v2.isObject());
+    CHECK_EQUAL(emptyTrapCallCount, 0);
+
+    // Enable debug mode
+    CHECK(JS_SetDebugMode(cx, true));
+
+    static const char trapClosureText[] = "some trap closure";
+
+    // scope JSScript  usage to make sure that it is not used after
+    // JS_ExecuteScript. This way we avoid using Anchor.
+    JS::RootedString trapClosure(cx);
+    {
+        jsbytecode *line2 = JS_LineNumberToPC(cx, script, 1);
+        CHECK(line2);
+
+        jsbytecode *line6 = JS_LineNumberToPC(cx, script, 5);
+        CHECK(line2);
+
+        trapClosure = JS_NewStringCopyZ(cx, trapClosureText);
+        CHECK(trapClosure);
+        JS::RootedValue closureValue(cx, JS::StringValue(trapClosure));
+        JS_SetTrap(cx, script, line2, EmptyTrapHandler, closureValue);
+        JS_SetTrap(cx, script, line6, EmptyTrapHandler, closureValue);
+
+        JS_GC(rt);
+
+        CHECK(JS_FlatStringEqualsAscii(JS_ASSERT_STRING_IS_FLAT(trapClosure), trapClosureText));
+    }
+
+    // execute
+    CHECK(JS_ExecuteScript(cx, global, script, &v2));
+    CHECK_EQUAL(emptyTrapCallCount, 11);
+
+    JS_GC(rt);
+
+    CHECK(JS_FlatStringEqualsAscii(JS_ASSERT_STRING_IS_FLAT(trapClosure), trapClosureText));
+
+    return true;
+}
+END_TEST(testTrap_gc)
+