Update Files

v8/include/cppgc/sentinel-pointer.h

@@ -0,0 +1,32 @@
+// Copyright 2021 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef INCLUDE_CPPGC_SENTINEL_POINTER_H_
+#define INCLUDE_CPPGC_SENTINEL_POINTER_H_
+
+#include <cstdint>
+
+namespace cppgc {
+namespace internal {
+
+// Special tag type used to denote some sentinel member. The semantics of the
+// sentinel is defined by the embedder.
+struct SentinelPointer {
+  static constexpr intptr_t kSentinelValue = 0b10;
+  template <typename T>
+  operator T*() const {
+    return reinterpret_cast<T*>(kSentinelValue);
+  }
+  // Hidden friends.
+  friend bool operator==(SentinelPointer, SentinelPointer) { return true; }
+  friend bool operator!=(SentinelPointer, SentinelPointer) { return false; }
+};
+
+}  // namespace internal
+
+constexpr internal::SentinelPointer kSentinelPointer;
+
+}  // namespace cppgc
+
+#endif  // INCLUDE_CPPGC_SENTINEL_POINTER_H_