1 // Copyright 2021 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef INCLUDE_CPPGC_SENTINEL_POINTER_H_
6 #define INCLUDE_CPPGC_SENTINEL_POINTER_H_
7 
8 #include <cstdint>
9 
10 namespace cppgc {
11 namespace internal {
12 
13 // Special tag type used to denote some sentinel member. The semantics of the
14 // sentinel is defined by the embedder.
15 struct SentinelPointer {
16   static constexpr intptr_t kSentinelValue = 0b10;
17   template <typename T>
operator T*cppgc::internal::SentinelPointer18   operator T*() const {
19     return reinterpret_cast<T*>(kSentinelValue);
20   }
21   // Hidden friends.
operator ==cppgc::internal::SentinelPointer22   friend bool operator==(SentinelPointer, SentinelPointer) { return true; }
operator !=cppgc::internal::SentinelPointer23   friend bool operator!=(SentinelPointer, SentinelPointer) { return false; }
24 };
25 
26 }  // namespace internal
27 
28 constexpr internal::SentinelPointer kSentinelPointer;
29 
30 }  // namespace cppgc
31 
32 #endif  // INCLUDE_CPPGC_SENTINEL_POINTER_H_
33