Remove Rooted<T> drop flag

This actually works, even though it feels too hacky...

src/jsapi_linux_32.rs

@@ -659,6 +659,7 @@ pub struct InternalHandle<T> {
     pub _phantom0: PhantomData<T>,
 }
 #[repr(C)]
+#[unsafe_no_drop_flag]
 pub struct Rooted<T> {
     pub _base: RootedBase<T>,
     pub stack: *mut *mut Rooted<*mut ::libc::c_void>,

src/jsapi_linux_64.rs

@@ -659,6 +659,7 @@ pub struct InternalHandle<T> {
     pub _phantom0: PhantomData<T>,
 }
 #[repr(C)]
+#[unsafe_no_drop_flag]
 pub struct Rooted<T> {
     pub _base: RootedBase<T>,
     pub stack: *mut *mut Rooted<*mut ::libc::c_void>,

src/jsapi_macos_64.rs

@@ -659,6 +659,7 @@ pub struct InternalHandle<T> {
     pub _phantom0: PhantomData<T>,
 }
 #[repr(C)]
+#[unsafe_no_drop_flag]
 pub struct Rooted<T> {
     pub _base: RootedBase<T>,
     pub stack: *mut *mut Rooted<*mut ::libc::c_void>,

src/jsapi_windows_gcc_64.rs

@@ -659,6 +659,7 @@ pub struct InternalHandle<T> {
     pub _phantom0: PhantomData<T>,
 }
 #[repr(C)]
+#[unsafe_no_drop_flag]
 pub struct Rooted<T> {
     pub _base: RootedBase<T>,
     pub stack: *mut *mut Rooted<*mut ::libc::c_void>,

src/lib.rs

@@ -10,6 +10,7 @@
 #![feature(str_utf16)]
 #![feature(unsafe_no_drop_flag)]
 #![feature(const_fn)]
+#![feature(filling_drop)]
 
 #![allow(non_upper_case_globals, non_camel_case_types, non_snake_case, improper_ctypes, raw_pointer_derive)]
 

src/rust.rs

@@ -328,16 +328,23 @@ impl<T: Copy> MutableHandle<T> {
     }
 }
 
-/*
 impl<T> Drop for Rooted<T> {
     fn drop(&mut self) {
         unsafe {
+            // Since we use no drop flags, we must check for a dropped value
+            // manually.
+            //
+            // see: https://github.com/rust-lang/rust/blob/master/src/libcore/mem.rs
+            if self.stack == mem::dropped::<*mut _>() &&
+               self.prev == mem::dropped::<*mut _> () {
+                return
+            }
+
             assert!(*self.stack == mem::transmute(&*self));
             *self.stack = self.prev;
         }
     }
 }
-*/
 
 impl CustomAutoRooter {
     pub fn new(cx: *mut JSContext, vftable: &'static _vftable_CustomAutoRooter)