1 files changed, 91 insertions, 0 deletions
diff --git a/js/public/RefCounted.h b/js/public/RefCounted.h
new file mode 100644
index 0000000000..86fe7eeb13
--- /dev/null
+++ b/js/public/RefCounted.h
@@ -0,0 +1,91 @@
+/* -*- 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/. */
+
+#ifndef js_RefCounted_h
+#define js_RefCounted_h
+
+#include "mozilla/Atomics.h"
+#include "mozilla/RefCountType.h"
+
+#include "js/Utility.h"
+
+// These types implement the same interface as mozilla::(Atomic)RefCounted and
+// must be used instead of mozilla::(Atomic)RefCounted for everything in
+// SpiderMonkey. There are two reasons:
+//  - Release() needs to call js_delete, not delete
+//  - SpiderMonkey does not have MOZILLA_INTERNAL_API defined which can lead
+//    to ODR violations that show up as spurious leak reports when ref-counted
+//    types are allocated by SpiderMonkey and released by Gecko (or vice versa).
+
+namespace js {
+
+template <typename T>
+class RefCounted {
+  static const MozRefCountType DEAD = 0xffffdead;
+
+ protected:
+  RefCounted() : mRefCnt(0) {}
+  ~RefCounted() { MOZ_ASSERT(mRefCnt == DEAD); }
+
+ public:
+  void AddRef() const {
+    MOZ_ASSERT(int32_t(mRefCnt) >= 0);
+    ++mRefCnt;
+  }
+
+  void Release() const {
+    MOZ_ASSERT(int32_t(mRefCnt) > 0);
+    MozRefCountType cnt = --mRefCnt;
+    if (0 == cnt) {
+#ifdef DEBUG
+      mRefCnt = DEAD;
+#endif
+      js_delete(const_cast<T*>(static_cast<const T*>(this)));
+    }
+  }
+
+ private:
+  mutable MozRefCountType mRefCnt;
+};
+
+template <typename T>
+class AtomicRefCounted {
+  // On 64-bit systems, if the refcount type is small (say, 32 bits), there's
+  // a risk that it could overflow.  So require it to be large enough.
+
+  static_assert(sizeof(MozRefCountType) == sizeof(uintptr_t),
+                "You're at risk for ref count overflow.");
+
+  static const MozRefCountType DEAD = ~MozRefCountType(0xffff) | 0xdead;
+
+ protected:
+  AtomicRefCounted() = default;
+  ~AtomicRefCounted() { MOZ_ASSERT(mRefCnt == DEAD); }
+
+ public:
+  void AddRef() const {
+    ++mRefCnt;
+    MOZ_ASSERT(mRefCnt != DEAD);
+  }
+
+  void Release() const {
+    MOZ_ASSERT(mRefCnt != 0);
+    MozRefCountType cnt = --mRefCnt;
+    if (0 == cnt) {
+#ifdef DEBUG
+      mRefCnt = DEAD;
+#endif
+      js_delete(const_cast<T*>(static_cast<const T*>(this)));
+    }
+  }
+
+ private:
+  mutable mozilla::Atomic<MozRefCountType> mRefCnt{0};
+};
+
+}  // namespace js
+
+#endif /* js_RefCounted_h */