diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/metadata-hook.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/metadata-hook.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,34 @@
+
+x = [1,2,3];
+setObjectMetadata(x, {y:0});
+assertEq(getObjectMetadata(x).y, 0);
+
+setObjectMetadataCallback(true);
+
+function Foo() {
+  this.x = 0;
+  this.y = 1;
+}
+
+function hello() {
+  function there() {
+    w = new Foo();
+    x = [1,2,3];
+    y = [2,3,5];
+    z = {a:0,b:1};
+  }
+  callee = there;
+  callee();
+}
+hello();
+
+var wc = getObjectMetadata(w).index;
+var xc = getObjectMetadata(x).index;
+var yc = getObjectMetadata(y).index;
+var zc = getObjectMetadata(z).index;
+
+assertEq(xc > wc, true);
+assertEq(yc > xc, true);
+assertEq(zc > yc, true);
+assertEq(getObjectMetadata(x).stack[0], callee);
+assertEq(getObjectMetadata(x).stack[1], hello);