diff -r 000000000000 -r 6474c204b198 js/jsd/test/test_jsval_retval.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/jsd/test/test_jsval_retval.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,42 @@
+// Bug 689101 - if the binary layout of jsval does not match between C and C++
+// code, then calls to functions returning jsval may get compiled differently
+// than the callee, resulting in parameters being shifted over by one.
+//
+// An example is where on Windows, calling jsdValue.getWrappedValue() will
+// return a random floating point number instead of an object.
+//
+// This test must be run with debugging already enabled
+
+function run_test() {
+    const Cc = Components.classes;
+    const Ci = Components.interfaces;
+    const DebuggerService = Cc["@mozilla.org/js/jsd/debugger-service;1"];
+    const jsdIDebuggerService = Ci.jsdIDebuggerService;
+    var jsd = DebuggerService.getService(jsdIDebuggerService);
+
+    do_check_true(jsd.isOn);
+
+    var n = 0;
+    function f() {
+        n++;
+    }
+
+    jsd.enumerateScripts({ enumerateScript: function(script) {
+        script.setBreakpoint(0);
+    } });
+
+    jsd.breakpointHook = function(frame, type, dummy) {
+        var scope = frame.scope;
+        var parent = scope.jsParent; // Probably does not need to be called
+        var wrapped = scope.getWrappedValue();
+        // Do not try to print 'wrapped'; it may be an internal Call object
+        // that will crash when you toString it. Different bug.
+        do_check_eq(typeof(wrapped), "object");
+        return Ci.jsdIExecutionHook.RETURN_CONTINUE;
+    };
+
+    f();
+
+    jsd.breakpointHook = null;
+    jsd = null;
+}