name : sentinel-pointer.h // 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> #include "cppgc/internal/api-constants.h" 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 { #if defined(CPPGC_POINTER_COMPRESSION) static constexpr intptr_t kSentinelValue = 1 << api_constants::kPointerCompressionShift; #else // !defined(CPPGC_POINTER_COMPRESSION) static constexpr intptr_t kSentinelValue = 0b10; #endif // !defined(CPPGC_POINTER_COMPRESSION) 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_