1 files changed, 99 insertions, 0 deletions
diff --git a/js/src/gc/Policy.h b/js/src/gc/Policy.h
new file mode 100644
index 0000000000..d30e4df379
--- /dev/null
+++ b/js/src/gc/Policy.h
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* JS Garbage Collector. */
+
+#ifndef gc_Policy_h
+#define gc_Policy_h
+
+#include <type_traits>
+
+#include "gc/Barrier.h"
+#include "gc/Marking.h"
+#include "js/GCPolicyAPI.h"
+
+namespace js {
+
+// Define the GCPolicy for all internal pointers.
+template <typename T>
+struct InternalGCPointerPolicy : public JS::GCPointerPolicy<T> {
+  using Type = std::remove_pointer_t<T>;
+
+#define IS_BASE_OF_OR(_1, BaseType, _2, _3) std::is_base_of_v<BaseType, Type> ||
+  static_assert(
+      JS_FOR_EACH_TRACEKIND(IS_BASE_OF_OR) false,
+      "InternalGCPointerPolicy must only be used for GC thing pointers");
+#undef IS_BASE_OF_OR
+
+  static void trace(JSTracer* trc, T* vp, const char* name) {
+    // It's not safe to trace unbarriered pointers except as part of root
+    // marking. If you get an assertion here you probably need to add a barrier,
+    // e.g. HeapPtr<T>.
+    TraceNullableRoot(trc, vp, name);
+  }
+};
+
+}  // namespace js
+
+namespace JS {
+
+// Internally, all pointer types are treated as pointers to GC things by
+// default.
+template <typename T>
+struct GCPolicy<T*> : public js::InternalGCPointerPolicy<T*> {};
+template <typename T>
+struct GCPolicy<T* const> : public js::InternalGCPointerPolicy<T* const> {};
+
+template <typename T>
+struct GCPolicy<js::HeapPtr<T>> {
+  static void trace(JSTracer* trc, js::HeapPtr<T>* thingp, const char* name) {
+    js::TraceNullableEdge(trc, thingp, name);
+  }
+  static bool needsSweep(js::HeapPtr<T>* thingp) {
+    return js::gc::IsAboutToBeFinalized(thingp);
+  }
+  static bool traceWeak(JSTracer* trc, js::HeapPtr<T>* thingp) {
+    return js::TraceWeakEdge(trc, thingp, "traceWeak");
+  }
+};
+
+template <typename T>
+struct GCPolicy<js::PreBarriered<T>> {
+  static void trace(JSTracer* trc, js::PreBarriered<T>* thingp,
+                    const char* name) {
+    js::TraceNullableEdge(trc, thingp, name);
+  }
+  static bool needsSweep(js::PreBarriered<T>* thingp) {
+    return js::gc::IsAboutToBeFinalized(thingp);
+  }
+};
+
+template <typename T>
+struct GCPolicy<js::WeakHeapPtr<T>> {
+  static void trace(JSTracer* trc, js::WeakHeapPtr<T>* thingp,
+                    const char* name) {
+    js::TraceEdge(trc, thingp, name);
+  }
+  static bool needsSweep(js::WeakHeapPtr<T>* thingp) {
+    return js::gc::IsAboutToBeFinalized(thingp);
+  }
+  static bool traceWeak(JSTracer* trc, js::WeakHeapPtr<T>* thingp) {
+    return js::TraceWeakEdge(trc, thingp, "traceWeak");
+  }
+};
+
+template <>
+struct GCPolicy<JS::GCCellPtr> {
+  static void trace(JSTracer* trc, JS::GCCellPtr* thingp, const char* name) {
+    // It's not safe to trace unbarriered pointers except as part of root
+    // marking.
+    js::TraceGCCellPtrRoot(trc, thingp, name);
+  }
+};
+
+}  // namespace JS
+
+#endif  // gc_Policy_h