servo: Merge #5543 - RootCollection: Start using RootedVec instead of SmallVec32 (from jagtalon:jag/slashdot); r=jdm

Partially fixes #5504.

Props to @ehegnes and @jdm for the help!

Source-Repo: https://github.com/servo/servo
Source-Revision: 184d214e260213bafc5801af33f3031289da9361

servo/components/script/dom/bindings/js.rs

@@ -50,6 +50,7 @@
 //!   `Option<Root<T>>` easy
 
 use dom::bindings::trace::JSTraceable;
+use dom::bindings::trace::RootedVec;
 use dom::bindings::utils::{Reflector, Reflectable};
 use dom::node::Node;
 use js::jsapi::JSObject;
@@ -57,11 +58,11 @@ use js::jsval::JSVal;
 use layout_interface::TrustedNodeAddress;
 use script_task::STACK_ROOTS;
 
-use util::smallvec::{SmallVec, SmallVec32};
-
 use core::nonzero::NonZero;
+use libc;
 use std::cell::{Cell, UnsafeCell};
 use std::default::Default;
+use std::intrinsics::return_address;
 use std::marker::PhantomData;
 use std::mem;
 use std::ops::Deref;
@@ -610,7 +611,7 @@ impl<T: Assignable<U>, U: Reflectable> TemporaryPushable<T> for Vec<JS<U>> {
 /// See also [*Exact Stack Rooting - Storing a GCPointer on the CStack*]
 /// (https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Internals/GC/Exact_Stack_Rooting).
 pub struct RootCollection {
-    roots: UnsafeCell<SmallVec32<*mut JSObject>>,
+    roots: UnsafeCell<RootedVec<*mut JSObject>>,
 }
 
 /// A pointer to a RootCollection, for use in global variables.
@@ -621,8 +622,12 @@ impl Copy for RootCollectionPtr {}
 impl RootCollection {
     /// Create an empty collection of roots
     pub fn new() -> RootCollection {
+        let addr = unsafe {
+            return_address() as *const libc::c_void
+        };
+
         RootCollection {
-            roots: UnsafeCell::new(SmallVec32::new()),
+            roots: UnsafeCell::new(RootedVec::new_with_destination_address(addr)),
         }
     }
 
@@ -632,7 +637,6 @@ impl RootCollection {
             let roots = self.roots.get();
             (*roots).push(untracked_js_ptr);
             debug!("  rooting {:?}", untracked_js_ptr);
-            assert!(!(*roots).spilled());
         }
     }
 

servo/components/script/dom/bindings/trace.rs

@@ -389,12 +389,21 @@ impl<T: VecRootableType> RootedVec<T> {
     /// Create a vector of items of type T that is rooted for
     /// the lifetime of this struct
     pub fn new() -> RootedVec<T> {
+        let addr = unsafe {
+            return_address() as *const libc::c_void
+        };
+
+        RootedVec::new_with_destination_address(addr)
+    }
+
+    /// Create a vector of items of type T. This constructor is specific
+    /// for RootCollection.
+    pub fn new_with_destination_address(addr: *const libc::c_void) -> RootedVec<T> {
         unsafe {
-            RootedCollectionSet::add::<T>(&*(return_address() as *const _));
+            RootedCollectionSet::add::<T>(&*(addr as *const _));
         }
         RootedVec::<T> { v: vec!() }
     }
-
 }
 
 #[unsafe_destructor]