1 // Copyright 2023 The Chromium Authors 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 BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_BASE_CXX20_IS_CONSTANT_EVALUATED_H_ 6 #define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_BASE_CXX20_IS_CONSTANT_EVALUATED_H_ 7 8 namespace partition_alloc::internal::base { 9 10 // std::is_constant_evaluated was introduced in C++20. PartitionAlloc's minimum 11 // supported C++ version is C++17. 12 #if defined(__cpp_lib_is_constant_evaluated) && \ 13 __cpp_lib_is_constant_evaluated >= 201811L 14 15 #include <type_traits> 16 using std::is_constant_evaluated; 17 18 #else 19 20 // Implementation of C++20's std::is_constant_evaluated. 21 // 22 // References: 23 // - https://en.cppreference.com/w/cpp/types/is_constant_evaluated 24 // - https://wg21.link/meta.const.eval 25 constexpr bool is_constant_evaluated() noexcept { 26 return __builtin_is_constant_evaluated(); 27 } 28 29 #endif 30 31 } // namespace partition_alloc::internal::base 32 33 #endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_BASE_CXX20_IS_CONSTANT_EVALUATED_H_ 34