Bug 1188197 - Allow PersistentRooted to store DynamicTraceable; r=sfink

js/public/RootingAPI.h

@@ -997,6 +997,10 @@ template<typename T>
 class PersistentRooted : public js::PersistentRootedBase<T>,
                          private mozilla::LinkedListElement<PersistentRooted<T>>
 {
+    static_assert(!mozilla::IsConvertible<T, StaticTraceable*>::value &&
+                  !mozilla::IsConvertible<T, DynamicTraceable*>::value,
+                  "Rooted takes pointer or Traceable types but not Traceable* type");
+
     typedef mozilla::LinkedListElement<PersistentRooted<T>> ListBase;
 
     friend class mozilla::LinkedList<PersistentRooted>;
@@ -1016,7 +1020,8 @@ class PersistentRooted : public js::PersistentRootedBase<T>,
                    kind == js::THING_ROOT_SCRIPT ||
                    kind == js::THING_ROOT_STRING ||
                    kind == js::THING_ROOT_ID ||
-                   kind == js::THING_ROOT_VALUE);
+                   kind == js::THING_ROOT_VALUE ||
+                   kind == js::THING_ROOT_DYNAMIC_TRACEABLE);
     }
 
   public:

js/src/gc/RootMarking.cpp

@@ -304,13 +304,14 @@ struct PersistentRootedMarker
 {
     typedef PersistentRooted<T> Element;
     typedef mozilla::LinkedList<Element> List;
-    typedef void (*MarkFunc)(JSTracer* trc, T* ref, const char* name);
+    using TraceFunc = void (*)(JSTracer* trc, T* ref, const char* name);
 
+    template <TraceFunction<T> TraceFn = TraceNullableRoot>
     static void
     markChain(JSTracer* trc, List& list, const char* name)
     {
         for (Element* r = list.getFirst(); r; r = r->getNext())
-            TraceNullableRoot(trc, r->address(), name);
+            TraceFn(trc, r->address(), name);
     }
 };
 
@@ -331,6 +332,11 @@ js::gc::MarkPersistentRootedChainsInLists(RootLists& roots, JSTracer* trc)
                                             "PersistentRooted<jsid>");
     PersistentRootedMarker<Value>::markChain(trc, roots.getPersistentRootedList<Value>(),
                                              "PersistentRooted<Value>");
+
+    PersistentRootedMarker<ConcreteTraceable>::markChain<MarkDynamicTraceable>(trc,
+        reinterpret_cast<mozilla::LinkedList<JS::PersistentRooted<ConcreteTraceable>>&>(
+            roots.heapRoots_[THING_ROOT_DYNAMIC_TRACEABLE]),
+        "PersistentRooted<Value>");
 }
 
 void

js/src/jsapi-tests/testGCExactRooting.cpp

@@ -123,6 +123,15 @@ struct RootedBase<DynamicContainer> {
     RelocatablePtrObject& obj() { return static_cast<Rooted<DynamicContainer>*>(this)->get().obj; }
     RelocatablePtrString& str() { return static_cast<Rooted<DynamicContainer>*>(this)->get().str; }
 };
+template <>
+struct PersistentRootedBase<DynamicContainer> {
+    RelocatablePtrObject& obj() {
+        return static_cast<PersistentRooted<DynamicContainer>*>(this)->get().obj;
+    }
+    RelocatablePtrString& str() {
+        return static_cast<PersistentRooted<DynamicContainer>*>(this)->get().str;
+    }
+};
 } // namespace js
 
 BEGIN_TEST(testGCRootedDynamicStructInternalStackStorage)
@@ -153,6 +162,40 @@ BEGIN_TEST(testGCRootedDynamicStructInternalStackStorageAugmented)
     JS::RootedObject obj(cx, container.obj());
     JS::RootedValue val(cx, StringValue(container.str()));
     CHECK(JS_SetProperty(cx, obj, "foo", val));
+    obj = nullptr;
+    val = UndefinedValue();
+
+    {
+        JS::RootedString actual(cx);
+        bool same;
+
+        // Automatic move from stack to heap.
+        JS::PersistentRooted<DynamicContainer> heap(cx, container);
+
+        // clear prior rooting.
+        container.obj() = nullptr;
+        container.str() = nullptr;
+
+        obj = heap.obj();
+        CHECK(JS_GetProperty(cx, obj, "foo", &val));
+        actual = val.toString();
+        CHECK(JS_StringEqualsAscii(cx, actual, "Hello", &same));
+        CHECK(same);
+        obj = nullptr;
+        actual = nullptr;
+
+        JS_GC(cx->runtime());
+        JS_GC(cx->runtime());
+
+        obj = heap.obj();
+        CHECK(JS_GetProperty(cx, obj, "foo", &val));
+        actual = val.toString();
+        CHECK(JS_StringEqualsAscii(cx, actual, "Hello", &same));
+        CHECK(same);
+        obj = nullptr;
+        actual = nullptr;
+    }
+
     return true;
 }
 END_TEST(testGCRootedDynamicStructInternalStackStorageAugmented)
@@ -232,6 +275,16 @@ BEGIN_TEST(testGCHandleHashMap)
 
     CHECK(CheckMyHashMap(cx, map));
 
+    // Unfortunately, the type of get() needs to be non-const ref, so
+    // we need to explicitly Move the storage.
+    JS::PersistentRooted<MyHashMap> heapMap(cx, mozilla::Move(map.get()));
+    CHECK(CheckMyHashMap(cx, heapMap));
+
+    JS_GC(rt);
+    JS_GC(rt);
+
+    CHECK(CheckMyHashMap(cx, heapMap));
+
     return true;
 }
 END_TEST(testGCHandleHashMap)

js/src/jsgc.cpp

@@ -1371,6 +1371,7 @@ js::gc::FinishPersistentRootedChains(RootLists& roots)
     FinishPersistentRootedChain(roots.getPersistentRootedList<JSString*>());
     FinishPersistentRootedChain(roots.getPersistentRootedList<jsid>());
     FinishPersistentRootedChain(roots.getPersistentRootedList<Value>());
+    FinishPersistentRootedChain(roots.heapRoots_[THING_ROOT_DYNAMIC_TRACEABLE]);
 }
 
 void