From e5a708f7272bffa925ed1c352775e41cfe010ed1 Mon Sep 17 00:00:00 2001
From: Tetsuharu OHZEKI <saneyuki.snyk@gmail.com>
Date: Sat, 14 Jun 2014 00:30:55 +0900
Subject: [PATCH] Make the conservertive stack scanner calculates
 `Temporary<T>` as root instead of calling root methods.

See: https://github.com/mozilla/servo/issues/2650
---
 src/components/script/dom/bindings/js.rs | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/src/components/script/dom/bindings/js.rs b/src/components/script/dom/bindings/js.rs
index 0f96f3e33e6..e2b2665c415 100644
--- a/src/components/script/dom/bindings/js.rs
+++ b/src/components/script/dom/bindings/js.rs
@@ -39,10 +39,10 @@
 /// - OptionalSettable: allows assigning Option values of JSRef/Temporary to fields of Option<JS<T>>
 /// - RootedReference: makes obtaining an Option<JSRef<T>> from an Option<Root<T>> easy
 
-use dom::bindings::utils::{Reflector, Reflectable, cx_for_dom_object};
+use dom::bindings::utils::{Reflector, Reflectable};
 use dom::node::Node;
 use dom::xmlhttprequest::{XMLHttpRequest, TrustedXHRAddress};
-use js::jsapi::{JSObject, JS_AddObjectRoot, JS_RemoveObjectRoot};
+use js::jsapi::JSObject;
 use layout_interface::TrustedNodeAddress;
 use script_task::StackRoots;
 
@@ -56,6 +56,8 @@ use std::mem;
 /// `JS<T>::assign` method or `OptionalSettable::assign` (for Option<JS<T>> fields).
 pub struct Temporary<T> {
     inner: JS<T>,
+    /// On-stack JS pointer to assuage conservative stack scanner
+    js_ptr: *mut JSObject,
 }
 
 impl<T> Eq for Temporary<T> {
@@ -64,25 +66,12 @@ impl<T> Eq for Temporary<T> {
     }
 }
 
-#[unsafe_destructor]
-impl<T: Reflectable> Drop for Temporary<T> {
-    fn drop(&mut self) {
-        let cx = cx_for_dom_object(&self.inner);
-        unsafe {
-            JS_RemoveObjectRoot(cx, self.inner.mut_reflector().rootable());
-        }
-    }
-}
-
 impl<T: Reflectable> Temporary<T> {
     /// Create a new Temporary value from a JS-owned value.
-    pub fn new(mut inner: JS<T>) -> Temporary<T> {
-        let cx = cx_for_dom_object(&inner);
-        unsafe {
-            JS_AddObjectRoot(cx, inner.mut_reflector().rootable());
-        }
+    pub fn new(inner: JS<T>) -> Temporary<T> {
         Temporary {
             inner: inner,
+            js_ptr: inner.reflector().get_jsobject(),
         }
     }