# 功能特性测试 (C++20)

< cpp

标准中为 C++11 和其后所引入的 C++ 语言和程序库的功能特性定义了一组预处理器宏。标准有意使之成为检测这些功能特性是否存在的一种简单且可移植的方式。

### 属性

`__has_cpp_attribute(` 属性记号 `)` |  |

检查（宏展开后） 属性记号 所指名的属性的存在。

对于标准属性，它将展开成该属性被添加到工作草案中时的年份和月份（见下表），特定于厂商的属性则以某个非零值确定。

能在 `#if` 与 `#elif` 的表达式中展开 `__has_cpp_attribute` 。 `#ifdef` 、 `#ifndef` 和 `defined` 把它当做已定义的宏，但不能在别处使用它。

属性记号 | 属性 | 值 | 标准
--- | --- | --- | ---
`carries_dependency` | `[[carries_dependency]]` | 200809L | (C++11)
`deprecated` | `[[deprecated]]` | 201309L | (C++14)
`fallthrough` | `[[fallthrough]]` | 201603L | (C++17)
`likely` | `[[likely]]` | 201803L | (C++20)
`maybe_unused` | `[[maybe_unused]]` | 201603L | (C++17)
`no_unique_address` | `[[no_unique_address]]` | 201803L | (C++20)
`nodiscard` | `[[nodiscard]]` | 201603L | (C++17)
201907L | (C++20)
`noreturn` | `[[noreturn]]` | 200809L | (C++11)
`unlikely` | `[[unlikely]]` | 201803L | (C++20)

### 语言功能特性

下列宏预定义于每个翻译单元。每个宏都展开成对应于相应功能特性被包含到工作草案时的年份与月份的整数字面量。

当功能特性发生了显著变更时，宏会相应地更新。

宏名 | 功能特性 | 值 | 标准
--- | --- | --- | ---
__cpp_aggregate_bases | 拥有基类的聚合类 | 201603L | (C++17)
__cpp_aggregate_nsdmi | 拥有默认成员初始化器的聚合类 | 201304L | (C++14)
__cpp_aggregate_paren_init | 形式为直接初始化的聚合初始化 | 201902L | (C++20)
__cpp_alias_templates | 别名模版 | 200704L | (C++11)
__cpp_aligned_new | 过对齐数据的动态内存分配 | 201606L | (C++17)
__cpp_attributes | 属性 | 200809L | (C++11)
__cpp_binary_literals | 二进制字面量 | 201304L | (C++14)
__cpp_capture_star_this | 以 `[=,*this]` 进行 `*this` 的按值 lambda 捕获 | 201603L | (C++17)
__cpp_char8_t | `char8_t` | 201811L | (C++20)
__cpp_concepts | 概念 | 201907L | (C++20)
__cpp_conditional_explicit | `explicit(bool)` | 201806L | (C++20)
__cpp_consteval | 立即函数 | 201811L | (C++20)
__cpp_constexpr | `constexpr` | 200704L | (C++11)
放松 constexpr 函数上的限制和及非 `const` 的 constexpr 非静态成员函数 | 201304L | (C++14)
Constexpr lambda | 201603L | (C++17)
constexpr 函数中的平凡默认初始化与汇编声明 | 201907L | (C++20)
constexpr 函数中的非字面变量、标签及 `goto` 语句 | 202110L | (C++23)
__cpp_constexpr_dynamic_alloc | constexpr 函数中的动态存储期操作 | 201907L | (C++20)
__cpp_constexpr_in_decltype | 在为常量求值所需要时生成函数和变量的定义 | 201711L | (C++20)
__cpp_constinit | `constinit` | 201907L | (C++20)
__cpp_coroutines | 协程 | 201902L | (C++20)
__cpp_decltype | `decltype` | 200707L | (C++11)
__cpp_decltype_auto | 常规函数的返回类型推导 | 201304L | (C++14)
__cpp_deduction_guides | 类模板的模板实参推导 | 201703L | (C++17)
聚合体与别名的 CTAD | 201907L | (C++20)
__cpp_delegating_constructors | 委托构造函数 | 200604L | (C++11)
__cpp_designated_initializers | 指派初始化器 | 201707L | (C++20)
__cpp_enumerator_attributes | 枚举项的属性 | 201411L | (C++17)
__cpp_explicit_this_parameter | 显式对象形参 | 202110L | (C++23)
__cpp_fold_expressions | 折叠表达式 | 201603L | (C++17)
__cpp_generic_lambdas | 泛型 lambda 表达式 | 201304L | (C++14)
泛型 lambda 的显式模板形参列表 | 201707L | (C++20)
__cpp_guaranteed_copy_elision | 通过简化值类别保证复制消除 | 201606L | (C++17)
__cpp_hex_float | 十六进制浮点字面量 | 201603L | (C++17)
__cpp_if_consteval | `consteval if` | 202106L | (C++23)
__cpp_if_constexpr | `constexpr if` | 201606L | (C++17)
__cpp_impl_coroutine | 协程（编译器支持） | 201902L | (C++20)
__cpp_impl_destroying_delete | 销毁的 `operator delete` （编译器支持） | 201806L | (C++20)
__cpp_impl_three_way_comparison | 三路比较（编译器支持） | 201907L | (C++20)
__cpp_inheriting_constructors | 继承构造函数 | 200802L | (C++11)
重述继承构造函数 | 201511L | (C++17)
__cpp_init_captures | Lambda 初始化捕获 | 201304L | (C++14)
Lambda 初始化捕获中的包展开 | 201803L | (C++20)
__cpp_initializer_lists | 列表初始化与 std::initializer_list | 200806L | (C++11)
__cpp_inline_variables | inline 变量 | 201606L | (C++17)
__cpp_lambdas | Lambda 表达式 | 200907L | (C++11)
__cpp_modules | 模块 | 201907L | (C++20)
__cpp_multidimensional_subscript | 多维下标运算符 | 202110L | (C++23)
__cpp_namespace_attributes | 命名空间的属性 | 201411L | (C++17)
__cpp_noexcept_function_type | 令异常规定为类型系统的一部分 | 201510L | (C++17)
__cpp_nontype_template_args | 允许全部非类型模板实参的常量求值 | 201411L | (C++17)
非类型模板形参中的类类型与浮点类型 | 201911L | (C++20)
__cpp_nontype_template_parameter_auto | 以 auto 声明非类型模板形参 | 201606L | (C++17)
__cpp_nsdmi | 非静态数据成员初始化器 | 200809L | (C++11)
__cpp_range_based_for | 基于范围的 for 循环 | 200907L | (C++11)
拥有相异的 `begin`/`end` 类型的基于范围的 `for` 循环 | 201603L | (C++17)
__cpp_raw_strings | 原始字符串字面量 | 200710L | (C++11)
__cpp_ref_qualifiers | 引用限定符 | 200710L | (C++11)
__cpp_return_type_deduction | 常规函数的返回类型推导 | 201304L | (C++14)
__cpp_rvalue_references | 右值引用 | 200610L | (C++11)
__cpp_size_t_suffix | `size_t` 与其有符号版本的字面量后缀 | 202011L | (C++23)
__cpp_sized_deallocation | 具大小解分配 | 201309L | (C++14)
__cpp_static_assert | `static_assert` | 200410L | (C++11)
单参数的 `static_assert` | 201411L | (C++17)
__cpp_structured_bindings | 结构化绑定 | 201606L | (C++17)
__cpp_template_template_args | 模板模板实参的匹配 | 201611L | (C++17)
__cpp_threadsafe_static_init | 带并发的动态初始化和销毁 | 200806L | (C++11)
__cpp_unicode_characters | 新字符类型（ char16_t 与 char32_t ） | 200704L | (C++11)
__cpp_unicode_literals | Unicode 字符串字面量 | 200710L | (C++11)
__cpp_user_defined_literals | 用户定义字面量 | 200809L | (C++11)
__cpp_using_enum | using enum | 201907L | (C++20)
__cpp_variable_templates | 变量模板 | 201304L | (C++14)
__cpp_variadic_templates | 变参模板 | 200704L | (C++11)
__cpp_variadic_using | using 声明中的包展开 | 201611L | (C++17)

### 标准库功能特性

如果包含了头文件 `<version>` 或下表中的任意对应头文件，则下列各个宏有定义。每个宏都展开成其对应的功能特性被包含于工作草案时的年份与月份的相应整数字面量。

当功能特性发生了显著变更时，宏会相应地更新。

宏名 | 功能特性 | 值 | 头文件 | 标准
--- | --- | --- | --- | ---
__cpp_lib_adaptor_iterator_pair_constructor | std::stack 与 std::queue 的迭代器对构造函数 | 202106L | `<stack>` `<queue>` | (C++23)
__cpp_lib_addressof_constexpr | constexpr std::addressof | 201603L | `<memory>` | (C++17)
__cpp_lib_allocate_at_least | std::allocate_at_least 等 | 202106L | `<memory>` | (C++23)
__cpp_lib_allocator_traits_is_always_equal | `std::allocator_traits::is_always_equal` | 201411L | `<memory>` `<scoped_allocator>` `<string>` `<deque>` `<forward_list>` `<list>` `<vector>` `<map>` `<set>` `<unordered_map>` `<unordered_set>` | (C++17)
__cpp_lib_any | std::any | 201606L | `<any>` | (C++17)
__cpp_lib_apply | std::apply | 201603L | `<tuple>` | (C++17)
__cpp_lib_array_constexpr | std::reverse_iterator 、 std::move_iterator 、 std::array 及范围访问的 constexpr | 201603L | `<iterator>` `<array>` | (C++17)
常量表达式迭代器 (ConstexprIterator) ； std::array 的 constexpr 比较；杂项 constexpr （ std::array::fill 等） | 201811L | `<iterator>` `<array>` | (C++20)
__cpp_lib_as_const | std::as_const | 201510L | `<utility>` | (C++17)
__cpp_lib_associative_heterogeneous_erasure | 关联容器与无序关联容器中的异质擦除 | 202110L | `<map>` `<set>` `<unordered_map>` `<unordered_set>` | (C++23)
__cpp_lib_assume_aligned | std::assume_aligned | 201811L | `<memory>` | (C++20)
__cpp_lib_atomic_flag_test | std::atomic_flag::test | 201907L | `<atomic>` | (C++20)
__cpp_lib_atomic_float | 浮点原子类型 | 201711L | `<atomic>` | (C++20)
__cpp_lib_atomic_is_always_lock_free | `constexpr atomic<T>::is_always_lock_free` | 201603L | `<atomic>` | (C++17)
__cpp_lib_atomic_lock_free_type_aliases | 原子免锁整数类型（ std::atomic_signed_lock_free 、 std::atomic_unsigned_lock_free ） | 201907L | `<atomic>` | (C++20)
__cpp_lib_atomic_ref | `std::atomic_ref` | 201806L | `<atomic>` | (C++20)
__cpp_lib_atomic_shared_ptr | `std::atomic<std::shared_ptr>` | 201711L | `<memory>` | (C++20)
__cpp_lib_atomic_value_initialization | 修正原子初始化（默认值初始化 std::atomic ） | 201911L | `<atomic>` `<memory>` | (C++20)
__cpp_lib_atomic_wait | 高效的 std::atomic 等待 | 201907L | `<atomic>` | (C++20)
__cpp_lib_barrier | `std::barrier` | 201907L | `<barrier>` | (C++20)
__cpp_lib_bind_front | `std::bind_front` | 201907L | `<functional>` | (C++20)
__cpp_lib_bit_cast | `std::bit_cast` | 201806L | `<bit>` | (C++20)
__cpp_lib_bitops | 位操作 | 201907L | `<bit>` | (C++20)
__cpp_lib_bool_constant | std::bool_constant | 201505L | `<type_traits>` | (C++17)
__cpp_lib_bounded_array_traits | `std::is_bounded_array` 、 `std::is_unbounded_array` | 201902L | `<type_traits>` | (C++20)
__cpp_lib_boyer_moore_searcher | std::boyer_moore_searcher|搜索器 | 201603L | `<functional>` | (C++17)
__cpp_lib_byte | `std::byte` | 201603L | `<cstddef>` | (C++17)
__cpp_lib_byteswap | `std::byteswap` | 202110L | `<bit>` | (C++23)
__cpp_lib_char8_t | char8_t 的库支持 | 201907L | `<atomic>` `<filesystem>` `<istream>` `<limits>` `<locale>` `<ostream>` `<string>` `<string_view>` | (C++20)
__cpp_lib_chrono | std::chrono::duration 与 std::chrono::time_point 的舍入函数 | 201510L | `<chrono>` | (C++17)
std::chrono::duration 与 std::chrono::time_point 的所有成员函数的 constexpr | 201611L | `<chrono>` | (C++17)
日历与时区 | 201907L | `<chrono>` | (C++20)
__cpp_lib_chrono_udls | 时间类型的用户定义字面量 | 201304L | `<chrono>` | (C++14)
__cpp_lib_clamp | std::clamp | 201603L | `<algorithm>` | (C++17)
__cpp_lib_complex_udls | `std::complex` 的用户定义字面量 | 201309L | `<complex>` | (C++14)
__cpp_lib_concepts | 标准库概念 | 202002L | `<concepts>` | (C++20)
__cpp_lib_constexpr_algorithms | 算法的 constexpr | 201806L | `<algorithm>` | (C++20)
__cpp_lib_constexpr_complex | std::complex 的 constexpr | 201711L | `<complex>` | (C++20)
__cpp_lib_constexpr_dynamic_alloc | std::allocator 与相关工具的 | 201907L | `<memory>` | (C++20)
__cpp_lib_constexpr_functional | 杂项 constexpr （ std::default_searcher ）； constexpr INVOKE | 201907L | `<functional>` | (C++20)
__cpp_lib_constexpr_iterator | 杂项 constexpr （ std::insert_iterator 等） | 201811L | `<iterator>` | (C++20)
__cpp_lib_constexpr_memory | std::pointer_traits 中的 constexpr | 201811L | `<memory>` | (C++20)
__cpp_lib_constexpr_numeric | <numeric> 算法的 constexpr | 201911L | `<numeric>` | (C++20)
__cpp_lib_constexpr_string | std::string 的 constexpr | 201907L | `<string>` | (C++20)
__cpp_lib_constexpr_string_view | 杂项 constexpr （ std::string_view::copy ） | 201811L | `<string_view>` | (C++20)
__cpp_lib_constexpr_tuple | 杂项 constexpr （ std::tuple::operator= 等） | 201811L | `<tuple>` | (C++20)
__cpp_lib_constexpr_typeinfo | std::type_info::operator== 的 constexpr | 202106L | `<typeinfo>` | (C++23)
__cpp_lib_constexpr_utility | 杂项 constexpr （ std::pair::operator= 等） | 201811L | `<utility>` | (C++20)
__cpp_lib_constexpr_vector | std::vector 的 constexpr | 201907L | `<vector>` | (C++20)
__cpp_lib_coroutine | 协程（库支持） | 201902L | `<coroutine>` | (C++20)
__cpp_lib_destroying_delete | 销毁的 `operator delete` （库支持） | 201806L | `<new>` | (C++20)
__cpp_lib_enable_shared_from_this | 再次启用 shared_from_this | 201603L | `<memory>` | (C++17)
__cpp_lib_endian | std::endian | 201907L | `<bit>` | (C++20)
__cpp_lib_erase_if | 统一容器擦除 | 202002L | `<string>` `<deque>` `<forward_list>` `<list>` `<vector>` `<map>` `<set>` `<unordered_map>` `<unordered_set>` | (C++20)
__cpp_lib_exchange_function | std::exchange | 201304L | `<utility>` | (C++14)
__cpp_lib_execution | 执行策略 | 201603L | `<execution>` | (C++17)
`std::execution::unsequenced_policy` | 201902L | `<execution>` | (C++20)
__cpp_lib_filesystem | 文件系统库 | 201703L | `<filesystem>` | (C++17)
__cpp_lib_format | 文本格式化 | 201907L | `<format>` | (C++20)
编译时格式字符串检查；减少 std::vformat_to 的参数化 | 202106L | `<format>` | (C++23)
修复 `chrono` 格式化器中的本地环境处理；格式化参数中使用转发引用 | 202110L | `<format>` | (C++23)
__cpp_lib_gcd_lcm | std::gcd、 std::lcm | 201606L | `<numeric>` | (C++17)
__cpp_lib_generic_associative_lookup | 关联容器中的异质比较查找 | 201304L | `<map>` `<set>` | (C++14)
__cpp_lib_generic_unordered_lookup | 无序关联容器中的异质比较查找 | 201811L | `<unordered_map>` `<unordered_set>` | (C++20)
__cpp_lib_hardware_interference_size | constexpr std::hardware_{constructive, destructive}_interference_size | 201703L | `<new>` | (C++17)
__cpp_lib_has_unique_object_representations | std::has_unique_object_representations | 201606L | `<type_traits>` | (C++17)
__cpp_lib_hypot | std::hypot 的 3 参数重载 | 201603L | `<cmath>` | (C++17)
__cpp_lib_incomplete_container_elements | 标准容器的最小不完整类型支持 | 201505L | `<forward_list>` `<list>` `<vector>` | (C++17)
__cpp_lib_int_pow2 | 整数的 2 的幂运算（ std::has_single_bit 、 std::bit_ceil 、 std::bit_floor 、 std::bit_length ） | 202002L | `<bit>` | (C++20)
__cpp_lib_integer_comparison_functions | 整数比较函数 | 202002L | `<utility>` | (C++20)
__cpp_lib_integer_sequence | 编译时整数序列 | 201304L | `<utility>` | (C++14)
__cpp_lib_integral_constant_callable | std::integral_constant::operator() | 201304L | `<type_traits>` | (C++14)
__cpp_lib_interpolate | `std::lerp` 与 `std::midpoint` | 201902L | `<cmath>` `<numeric>` | (C++20)
__cpp_lib_invoke | std::invoke() | 201411L | `<functional>` | (C++17)
__cpp_lib_invoke_r | `std::invoke_r` | 202106L | `<functional>` | (C++23)
__cpp_lib_is_aggregate | `std::is_aggregate` | 201703L | `<type_traits>` | (C++17)
__cpp_lib_is_constant_evaluated | `std::is_constant_evaluated` | 201811L | `<type_traits>` | (C++20)
__cpp_lib_is_final | std::is_final | 201402L | `<type_traits>` | (C++14)
__cpp_lib_is_invocable | std::is_invocable 、 std::invoke_result | 201703L | `<type_traits>` | (C++17)
__cpp_lib_is_layout_compatible | `std::is_layout_compatible` | 201907L | `<type_traits>` | (C++20)
__cpp_lib_is_nothrow_convertible | `std::is_nothrow_convertible` | 201806L | `<type_traits>` | (C++20)
__cpp_lib_is_null_pointer | std::is_null_pointer | 201309L | `<type_traits>` | (C++14)
__cpp_lib_is_pointer_interconvertible | 指针可互转换特征 | 201907L | `<type_traits>` | (C++20)
__cpp_lib_is_scoped_enum | `std::is_scoped_enum` | 202011L | `<type_traits>` | (C++23)
__cpp_lib_is_swappable | [nothrow-]swappable 特征 | 201603L | `<type_traits>` | (C++17)
__cpp_lib_jthread | 停止记号与结合线程 | 201911L | `<stop_token>` `<thread>` | (C++20)
__cpp_lib_latch | `std::latch` | 201907L | `<latch>` | (C++20)
__cpp_lib_launder | 核心问题 1776 ：替换含引用成员的类对象（ std::launder ） | 201606L | `<new>` | (C++17)
__cpp_lib_list_remove_return_type | 更改 std::forward_list 与 std::list remove() 、 remove_if() 及 unique() 成员的返回类型 | 201806L | `<forward_list>` `<list>` | (C++20)
__cpp_lib_logical_traits | 逻辑运算符类型特征 | 201510L | `<type_traits>` | (C++17)
__cpp_lib_make_from_tuple | std::make_from_tuple() | 201606L | `<tuple>` | (C++17)
__cpp_lib_make_reverse_iterator | `std::make_reverse_iterator` | 201402L | `<iterator>` | (C++14)
__cpp_lib_make_unique | std::make_unique | 201304L | `<memory>` | (C++14)
__cpp_lib_map_try_emplace | std::map::try_emplace, std::map::insert_or_assign | 201411L | `<map>` | (C++17)
__cpp_lib_math_constants | 数学常数 | 201907L | `<numbers>` | (C++20)
__cpp_lib_math_special_functions | C++17 的数学特殊函数 | 201603L | `<cmath>` | (C++17)
__cpp_lib_memory_resource | std::pmr::memory_resource | 201603L | `<memory_resource>` | (C++17)
__cpp_lib_monadic_optional | std::optional 中的单子操作 | 202110L | `<optional>` | (C++23)
__cpp_lib_move_only_function | std::move_only_function | 202110L | `<functional>` | (C++23)
__cpp_lib_node_extract | 拼接 map 与 set （ std::map::extract 、 std::map::merge 、 `std::map::insert(node_type)` 等） | 201606L | `<map>` `<set>` `<unordered_map>` `<unordered_set>` | (C++17)
__cpp_lib_nonmember_container_access | std::size() 、 std::data() 及 std::empty() | 201411L | `<iterator>` `<array>` `<deque>` `<forward_list>` `<list>` `<map>` `<regex>` `<set>` `<string>` `<unordered_map>` `<unordered_set>` `<vector>` | (C++17)
__cpp_lib_not_fn | std::not_fn() | 201603L | `<functional>` | (C++17)
__cpp_lib_null_iterators | 空老式向前迭代器 (LegacyForwardIterator) | 201304L | `<iterator>` | (C++14)
__cpp_lib_optional | std::optional | 201606L | `<optional>` | (C++17)
完全 `constexpr` std::optional | 202106L | `<optional>` | (C++23)
__cpp_lib_out_ptr | std::out_ptr、 std::inout_ptr | 202106L | `<memory>` | (C++23)
__cpp_lib_parallel_algorithm | 并行算法 | 201603L | `<algorithm>` `<numeric>` | (C++17)
__cpp_lib_polymorphic_allocator | std::pmr::polymorphic_allocator<> 作为词汇类型 | 201902L | `<memory_resource>` | (C++20)
__cpp_lib_quoted_string_io | std::quoted | 201304L | `<iomanip>` | (C++14)
__cpp_lib_ranges | 范围库与受约束算法 | 201911L | `<algorithm>` `<functional>` `<iterator>` `<memory>` `<ranges>` | (C++20)
不可默认初始化的视图 | 202106L | (C++23)
带所有权的视图 | 202110L | (C++23)
__cpp_lib_ranges_starts_ends_with | std::ranges::starts_with、 std::ranges::ends_with | 202106L | `<algorithm>` | (C++23)
__cpp_lib_ranges_zip | std::ranges::zip_view、 std::ranges::zip_transform_view、 std::ranges::adjacent_view、 std::ranges::adjacent_transform_view | 202110L | `<ranges>` `<tuple>` `<utility>` | (C++23)
__cpp_lib_raw_memory_algorithms | 扩展内存管理工具 | 201606L | `<memory>` | (C++17)
__cpp_lib_remove_cvref | `std::remove_cvref` | 201711L | `<type_traits>` | (C++20)
__cpp_lib_result_of_sfinae | std::result_of 与 SFINAE | 201210L | `<type_traits>` `<functional>` | (C++14)
__cpp_lib_robust_nonmodifying_seq_ops | 使不修改序列的操作更稳健（ std::mismatch 、 std::equal 及 std::is_permutation 的双范围重载） | 201304L | `<algorithm>` | (C++14)
__cpp_lib_sample | std::sample | 201603L | `<algorithm>` | (C++17)
__cpp_lib_scoped_lock | `std::scoped_lock` | 201703L | `<mutex>` | (C++17)
__cpp_lib_semaphore | `std::counting_semaphore` 、 `std::binary_semaphore` | 201907L | `<semaphore>` | (C++20)
__cpp_lib_shared_mutex | std::shared_mutex （无时限） | 201505L | `<shared_mutex>` | (C++17)
__cpp_lib_shared_ptr_arrays | std::shared_ptr<T[]> | 201611L | `<memory>` | (C++17)
std::make_shared 的数组支持 | 201707L | `<memory>` | (C++20)
__cpp_lib_shared_ptr_weak_type | `shared_ptr::weak_type` | 201606L | `<memory>` | (C++17)
__cpp_lib_shared_timed_mutex | std::shared_timed_mutex | 201402L | `<shared_mutex>` | (C++14)
__cpp_lib_shift | `std::shift_left` 与 `std::shift_right` | 201806L | `<algorithm>` | (C++20)
__cpp_lib_smart_ptr_for_overwrite | 用默认初始化创建智能指针（ std::allocate_shared_for_overwrite 、 std::make_shared_for_overwrite 、 std::make_unique_for_overwrite ） | 201811L | `<memory>` | (C++20)
__cpp_lib_source_location | 源码信息捕获（ std::source_location ） | 201907L | `<source_location>` | (C++20)
__cpp_lib_span | `std::span` | 202002L | `<span>` | (C++20)
__cpp_lib_spanstream | `std::spanbuf`、 `std::spanstream` | 202106L | `<spanstream>` | (C++23)
__cpp_lib_ssize | `std::ssize` 与无符号的 `std::span::size` | 201902L | `<iterator>` | (C++20)
__cpp_lib_stacktrace | 栈踪库 | 202011L | `<stacktrace>` | (C++23)
__cpp_lib_starts_ends_with | 字符串前缀与后缀检查（ std::string 与 std::string_view 的 starts_with() 与 ends_with() ） | 201711L | `<string>` `<string_view>` | (C++20)
__cpp_lib_stdatomic_h | C 原子操作的兼容头文件 | 202011L | `<stdatomic.h>` | (C++23)
__cpp_lib_string_contains | `std::basic_string` 与 `std::basic_string_view` 的 `contains` 函数 | 202011L | `<string>` `<string_view>` | (C++23)
__cpp_lib_string_resize_and_overwrite | std::basic_string::resize_and_overwrite | 202110L | `<string>` | (C++23)
__cpp_lib_string_udls | 字符串类型的用户定义字面量 | 201304L | `<string>` | (C++14)
__cpp_lib_string_view | std::string_view | 201606L | `<string>` `<string_view>` | (C++17)
常量表达式迭代器 (ConstexprIterator) | 201803L | `<string>` `<string_view>` | (C++20)
__cpp_lib_syncbuf | 同步缓冲的输出流（ std::syncbuf 、 std::osyncstream ）与操纵符 | 201803L | `<syncstream>` | (C++20)
__cpp_lib_three_way_comparison | 三路比较（库支持）；添加三路比较到标准库 | 201907L | `<compare>` | (C++20)
__cpp_lib_to_address | 转换指针为裸指针（ std::to_address ） | 201711L | `<memory>` | (C++20)
__cpp_lib_to_array | `std::to_array` | 201907L | `<array>` | (C++20)
__cpp_lib_to_chars | 初等字符串转换（ std::to_chars 、 std::from_chars ） | 201611L | `<charconv>` | (C++17)
__cpp_lib_to_underlying | `std::to_underlying` | 202102L | `<utility>` | (C++23)
__cpp_lib_transformation_trait_aliases | 变换特征的别名模板 | 201304L | `<type_traits>` | (C++14)
__cpp_lib_transparent_operators | 通透运算符函数对象（ std::less<> 等） | 201210L | `<functional>` | (C++14)
通透的 std::owner_less （ `std::owner_less<void>` ） | 201510L | `<memory>` `<functional>` | (C++17)
__cpp_lib_tuple_element_t | `std::tuple_element_t` | 201402L | `<tuple>` | (C++14)
__cpp_lib_tuples_by_type | 按类型寻址 tuple | 201304L | `<tuple>` `<utility>` | (C++14)
__cpp_lib_type_identity | std::type_identity | 201806L | `<type_traits>` | (C++20)
__cpp_lib_type_trait_variable_templates | 类型特征变量模板（ std::is_void_v 等） | 201510L | `<type_traits>` | (C++17)
__cpp_lib_uncaught_exceptions | `std::uncaught_exceptions` | 201411L | `<exception>` | (C++17)
__cpp_lib_unordered_map_try_emplace | std::unordered_map::try_emplace 、 std::unordered_map::insert_or_assign | 201411L | `<unordered_map>` | (C++17)
__cpp_lib_unwrap_ref | std::unwrap_ref_decay 与 std::unwrap_reference | 201811L | `<type_traits>` | (C++20)
__cpp_lib_variant | std::variant ： C++17 的类型安全联合体 | 201606L | `<variant>` | (C++17)
std::variant 的派生类的 std::visit | 202102L | `<variant>` | (C++23)
完全 `constexpr` std::variant | 202106L | `<variant>` | (C++23)
__cpp_lib_void_t | std::void_t | 201411L | `<type_traits>` | (C++17)

### 示例

#### 正常使用

    #ifdef __has_include                           // 检查 __has_include 是否存在
    #  if __has_include(<optional>)                // 检查标准库
    #    include <optional>
    #  elif __has_include(<experimental/optional>) // 检查实验版本
    #    include <experimental/optional>
    #  elif __has_include(<boost/optional.hpp>)    // 尝试外部库
    #    include <boost/optional.hpp>
    #  else                                        // 完全找不到
    #     error "Missing <optional>"
    #  endif
    #endif

    #ifdef __has_cpp_attribute                      // 检查 __has_cpp_attribute 是否存在
    #  if __has_cpp_attribute(deprecated)           // 检查一个属性
    #    define DEPRECATED(msg) [[deprecated(msg)]]
    #  endif
    #endif
    #ifndef DEPRECATED
    #    define DEPRECATED(msg)
    #endif

    DEPRECATED("foo() has been deprecated") void foo();

    #if __cpp_constexpr >= 201304                   // 检查功能特性的指定版本
    #  define CONSTEXPR constexpr
    #else
    #  define CONSTEXPR inline
    #endif

    CONSTEXPR int bar(unsigned i)
    {
    #ifdef __cpp_binary_literals                    // 检查功能特性是否存在
        unsigned mask1 = 0b11000000;
        unsigned mask2 = 0b00000111;
    #else
        unsigned mask1 = 0xA0;
        unsigned mask2 = 0x07;
    #endif
        if ( i & mask1 )
            return 1;
        if ( i & mask2 )
            return 2;
        return 0;
    }

    int main()
    {
    }

#### 编译器功能特性放出

以下示例放出 C++ 编译器功能特性与属性。

    #if __cplusplus < 201100
    #  error "C++11 or better is required"
    #endif

    #include <algorithm>
    #include <cstring>
    #include <iomanip>
    #include <iostream>
    #include <string>

    #ifdef __has_include
    # if __has_include(<version>)
    #   include <version>
    # endif
    #endif

    #define COMPILER_FEATURE_VALUE(value) #value
    #define COMPILER_FEATURE_ENTRY(name) { #name, COMPILER_FEATURE_VALUE(name) },

    #ifdef __has_cpp_attribute
    # define COMPILER_ATTRIBUTE_VALUE_AS_STRING(s) #s
    # define COMPILER_ATTRIBUTE_AS_NUMBER(x) COMPILER_ATTRIBUTE_VALUE_AS_STRING(x)
    # define COMPILER_ATTRIBUTE_ENTRY(attr) \
      { #attr, COMPILER_ATTRIBUTE_AS_NUMBER(__has_cpp_attribute(attr)) },
    #else
    # define COMPILER_ATTRIBUTE_ENTRY(attr) { #attr, "_" },
    #endif

    // 更改这些选项以仅打印所需的信息。
    static struct PrintOptions {
        constexpr static bool titles               = 1;
        constexpr static bool attributes           = 1;
        constexpr static bool general_features     = 1;
        constexpr static bool core_features        = 1;
        constexpr static bool lib_features         = 1;
        constexpr static bool supported_features   = 1;
        constexpr static bool unsupported_features = 1;
        constexpr static bool sorted_by_value      = 0;
        constexpr static bool cxx11                = 1;
        constexpr static bool cxx14                = 1;
        constexpr static bool cxx17                = 1;
        constexpr static bool cxx20                = 1;
        constexpr static bool cxx23                = 1;
    }   print;

    struct CompilerFeature {
        CompilerFeature(const char* name = nullptr, const char* value = nullptr)
            : name(name), value(value) {}
        const char* name; const char* value;
    };

    static CompilerFeature cxx[] = {
    COMPILER_FEATURE_ENTRY(__cplusplus)
    COMPILER_FEATURE_ENTRY(__cpp_exceptions)
    COMPILER_FEATURE_ENTRY(__cpp_rtti)
    #if 0
    COMPILER_FEATURE_ENTRY(__GNUC__)
    COMPILER_FEATURE_ENTRY(__GNUC_MINOR__)
    COMPILER_FEATURE_ENTRY(__GNUC_PATCHLEVEL__)
    COMPILER_FEATURE_ENTRY(__GNUG__)
    COMPILER_FEATURE_ENTRY(__clang__)
    COMPILER_FEATURE_ENTRY(__clang_major__)
    COMPILER_FEATURE_ENTRY(__clang_minor__)
    COMPILER_FEATURE_ENTRY(__clang_patchlevel__)
    #endif
    };
    static CompilerFeature cxx11[] = {
    COMPILER_FEATURE_ENTRY(__cpp_alias_templates)
    COMPILER_FEATURE_ENTRY(__cpp_attributes)
    COMPILER_FEATURE_ENTRY(__cpp_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_decltype)
    COMPILER_FEATURE_ENTRY(__cpp_delegating_constructors)
    COMPILER_FEATURE_ENTRY(__cpp_inheriting_constructors)
    COMPILER_FEATURE_ENTRY(__cpp_initializer_lists)
    COMPILER_FEATURE_ENTRY(__cpp_lambdas)
    COMPILER_FEATURE_ENTRY(__cpp_nsdmi)
    COMPILER_FEATURE_ENTRY(__cpp_range_based_for)
    COMPILER_FEATURE_ENTRY(__cpp_raw_strings)
    COMPILER_FEATURE_ENTRY(__cpp_ref_qualifiers)
    COMPILER_FEATURE_ENTRY(__cpp_rvalue_references)
    COMPILER_FEATURE_ENTRY(__cpp_static_assert)
    COMPILER_FEATURE_ENTRY(__cpp_threadsafe_static_init)
    COMPILER_FEATURE_ENTRY(__cpp_unicode_characters)
    COMPILER_FEATURE_ENTRY(__cpp_unicode_literals)
    COMPILER_FEATURE_ENTRY(__cpp_user_defined_literals)
    COMPILER_FEATURE_ENTRY(__cpp_variadic_templates)
    };
    static CompilerFeature cxx14[] = {
    COMPILER_FEATURE_ENTRY(__cpp_aggregate_nsdmi)
    COMPILER_FEATURE_ENTRY(__cpp_binary_literals)
    COMPILER_FEATURE_ENTRY(__cpp_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_decltype_auto)
    COMPILER_FEATURE_ENTRY(__cpp_generic_lambdas)
    COMPILER_FEATURE_ENTRY(__cpp_init_captures)
    COMPILER_FEATURE_ENTRY(__cpp_return_type_deduction)
    COMPILER_FEATURE_ENTRY(__cpp_sized_deallocation)
    COMPILER_FEATURE_ENTRY(__cpp_variable_templates)
    };
    static CompilerFeature cxx14lib[] = {
    COMPILER_FEATURE_ENTRY(__cpp_lib_chrono_udls)
    COMPILER_FEATURE_ENTRY(__cpp_lib_complex_udls)
    COMPILER_FEATURE_ENTRY(__cpp_lib_exchange_function)
    COMPILER_FEATURE_ENTRY(__cpp_lib_generic_associative_lookup)
    COMPILER_FEATURE_ENTRY(__cpp_lib_integer_sequence)
    COMPILER_FEATURE_ENTRY(__cpp_lib_integral_constant_callable)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_final)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_null_pointer)
    COMPILER_FEATURE_ENTRY(__cpp_lib_make_reverse_iterator)
    COMPILER_FEATURE_ENTRY(__cpp_lib_make_unique)
    COMPILER_FEATURE_ENTRY(__cpp_lib_null_iterators)
    COMPILER_FEATURE_ENTRY(__cpp_lib_quoted_string_io)
    COMPILER_FEATURE_ENTRY(__cpp_lib_result_of_sfinae)
    COMPILER_FEATURE_ENTRY(__cpp_lib_robust_nonmodifying_seq_ops)
    COMPILER_FEATURE_ENTRY(__cpp_lib_shared_timed_mutex)
    COMPILER_FEATURE_ENTRY(__cpp_lib_string_udls)
    COMPILER_FEATURE_ENTRY(__cpp_lib_transformation_trait_aliases)
    COMPILER_FEATURE_ENTRY(__cpp_lib_transparent_operators)
    COMPILER_FEATURE_ENTRY(__cpp_lib_tuple_element_t)
    COMPILER_FEATURE_ENTRY(__cpp_lib_tuples_by_type)
    };

    static CompilerFeature cxx17[] = {
    COMPILER_FEATURE_ENTRY(__cpp_aggregate_bases)
    COMPILER_FEATURE_ENTRY(__cpp_aligned_new)
    COMPILER_FEATURE_ENTRY(__cpp_capture_star_this)
    COMPILER_FEATURE_ENTRY(__cpp_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_deduction_guides)
    COMPILER_FEATURE_ENTRY(__cpp_enumerator_attributes)
    COMPILER_FEATURE_ENTRY(__cpp_fold_expressions)
    COMPILER_FEATURE_ENTRY(__cpp_guaranteed_copy_elision)
    COMPILER_FEATURE_ENTRY(__cpp_hex_float)
    COMPILER_FEATURE_ENTRY(__cpp_if_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_inheriting_constructors)
    COMPILER_FEATURE_ENTRY(__cpp_inline_variables)
    COMPILER_FEATURE_ENTRY(__cpp_namespace_attributes)
    COMPILER_FEATURE_ENTRY(__cpp_noexcept_function_type)
    COMPILER_FEATURE_ENTRY(__cpp_nontype_template_args)
    COMPILER_FEATURE_ENTRY(__cpp_nontype_template_parameter_auto)
    COMPILER_FEATURE_ENTRY(__cpp_range_based_for)
    COMPILER_FEATURE_ENTRY(__cpp_static_assert)
    COMPILER_FEATURE_ENTRY(__cpp_structured_bindings)
    COMPILER_FEATURE_ENTRY(__cpp_template_template_args)
    COMPILER_FEATURE_ENTRY(__cpp_variadic_using)
    };
    static CompilerFeature cxx17lib[] = {
    COMPILER_FEATURE_ENTRY(__cpp_lib_addressof_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_lib_allocator_traits_is_always_equal)
    COMPILER_FEATURE_ENTRY(__cpp_lib_any)
    COMPILER_FEATURE_ENTRY(__cpp_lib_apply)
    COMPILER_FEATURE_ENTRY(__cpp_lib_array_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_lib_as_const)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_is_always_lock_free)
    COMPILER_FEATURE_ENTRY(__cpp_lib_bool_constant)
    COMPILER_FEATURE_ENTRY(__cpp_lib_boyer_moore_searcher)
    COMPILER_FEATURE_ENTRY(__cpp_lib_byte)
    COMPILER_FEATURE_ENTRY(__cpp_lib_chrono)
    COMPILER_FEATURE_ENTRY(__cpp_lib_clamp)
    COMPILER_FEATURE_ENTRY(__cpp_lib_enable_shared_from_this)
    COMPILER_FEATURE_ENTRY(__cpp_lib_execution)
    COMPILER_FEATURE_ENTRY(__cpp_lib_filesystem)
    COMPILER_FEATURE_ENTRY(__cpp_lib_gcd_lcm)
    COMPILER_FEATURE_ENTRY(__cpp_lib_hardware_interference_size)
    COMPILER_FEATURE_ENTRY(__cpp_lib_has_unique_object_representations)
    COMPILER_FEATURE_ENTRY(__cpp_lib_hypot)
    COMPILER_FEATURE_ENTRY(__cpp_lib_incomplete_container_elements)
    COMPILER_FEATURE_ENTRY(__cpp_lib_invoke)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_aggregate)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_invocable)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_swappable)
    COMPILER_FEATURE_ENTRY(__cpp_lib_launder)
    COMPILER_FEATURE_ENTRY(__cpp_lib_logical_traits)
    COMPILER_FEATURE_ENTRY(__cpp_lib_make_from_tuple)
    COMPILER_FEATURE_ENTRY(__cpp_lib_map_try_emplace)
    COMPILER_FEATURE_ENTRY(__cpp_lib_math_special_functions)
    COMPILER_FEATURE_ENTRY(__cpp_lib_memory_resource)
    COMPILER_FEATURE_ENTRY(__cpp_lib_node_extract)
    COMPILER_FEATURE_ENTRY(__cpp_lib_nonmember_container_access)
    COMPILER_FEATURE_ENTRY(__cpp_lib_not_fn)
    COMPILER_FEATURE_ENTRY(__cpp_lib_optional)
    COMPILER_FEATURE_ENTRY(__cpp_lib_parallel_algorithm)
    COMPILER_FEATURE_ENTRY(__cpp_lib_raw_memory_algorithms)
    COMPILER_FEATURE_ENTRY(__cpp_lib_sample)
    COMPILER_FEATURE_ENTRY(__cpp_lib_scoped_lock)
    COMPILER_FEATURE_ENTRY(__cpp_lib_shared_mutex)
    COMPILER_FEATURE_ENTRY(__cpp_lib_shared_ptr_arrays)
    COMPILER_FEATURE_ENTRY(__cpp_lib_shared_ptr_weak_type)
    COMPILER_FEATURE_ENTRY(__cpp_lib_string_view)
    COMPILER_FEATURE_ENTRY(__cpp_lib_to_chars)
    COMPILER_FEATURE_ENTRY(__cpp_lib_transparent_operators)
    COMPILER_FEATURE_ENTRY(__cpp_lib_type_trait_variable_templates)
    COMPILER_FEATURE_ENTRY(__cpp_lib_uncaught_exceptions)
    COMPILER_FEATURE_ENTRY(__cpp_lib_unordered_map_try_emplace)
    COMPILER_FEATURE_ENTRY(__cpp_lib_variant)
    COMPILER_FEATURE_ENTRY(__cpp_lib_void_t)
    };

    static CompilerFeature cxx20[] = {
    COMPILER_FEATURE_ENTRY(__cpp_aggregate_paren_init)
    COMPILER_FEATURE_ENTRY(__cpp_char8_t)
    COMPILER_FEATURE_ENTRY(__cpp_concepts)
    COMPILER_FEATURE_ENTRY(__cpp_conditional_explicit)
    COMPILER_FEATURE_ENTRY(__cpp_consteval)
    COMPILER_FEATURE_ENTRY(__cpp_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_constexpr_dynamic_alloc)
    COMPILER_FEATURE_ENTRY(__cpp_constexpr_in_decltype)
    COMPILER_FEATURE_ENTRY(__cpp_constinit)
    COMPILER_FEATURE_ENTRY(__cpp_deduction_guides)
    COMPILER_FEATURE_ENTRY(__cpp_designated_initializers)
    COMPILER_FEATURE_ENTRY(__cpp_generic_lambdas)
    COMPILER_FEATURE_ENTRY(__cpp_impl_coroutine)
    COMPILER_FEATURE_ENTRY(__cpp_impl_destroying_delete)
    COMPILER_FEATURE_ENTRY(__cpp_impl_three_way_comparison)
    COMPILER_FEATURE_ENTRY(__cpp_init_captures)
    COMPILER_FEATURE_ENTRY(__cpp_modules)
    COMPILER_FEATURE_ENTRY(__cpp_nontype_template_args)
    COMPILER_FEATURE_ENTRY(__cpp_using_enum)
    };
    static CompilerFeature cxx20lib[] = {
    COMPILER_FEATURE_ENTRY(__cpp_lib_array_constexpr)
    COMPILER_FEATURE_ENTRY(__cpp_lib_assume_aligned)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_flag_test)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_float)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_lock_free_type_aliases)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_ref)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_shared_ptr)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_value_initialization)
    COMPILER_FEATURE_ENTRY(__cpp_lib_atomic_wait)
    COMPILER_FEATURE_ENTRY(__cpp_lib_barrier)
    COMPILER_FEATURE_ENTRY(__cpp_lib_bind_front)
    COMPILER_FEATURE_ENTRY(__cpp_lib_bit_cast)
    COMPILER_FEATURE_ENTRY(__cpp_lib_bitops)
    COMPILER_FEATURE_ENTRY(__cpp_lib_bounded_array_traits)
    COMPILER_FEATURE_ENTRY(__cpp_lib_char8_t)
    COMPILER_FEATURE_ENTRY(__cpp_lib_chrono)
    COMPILER_FEATURE_ENTRY(__cpp_lib_concepts)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_algorithms)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_complex)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_dynamic_alloc)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_functional)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_iterator)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_memory)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_numeric)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_string)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_string_view)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_tuple)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_utility)
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_vector)
    COMPILER_FEATURE_ENTRY(__cpp_lib_coroutine)
    COMPILER_FEATURE_ENTRY(__cpp_lib_destroying_delete)
    COMPILER_FEATURE_ENTRY(__cpp_lib_endian)
    COMPILER_FEATURE_ENTRY(__cpp_lib_erase_if)
    COMPILER_FEATURE_ENTRY(__cpp_lib_execution)
    COMPILER_FEATURE_ENTRY(__cpp_lib_format)
    COMPILER_FEATURE_ENTRY(__cpp_lib_generic_unordered_lookup)
    COMPILER_FEATURE_ENTRY(__cpp_lib_int_pow2)
    COMPILER_FEATURE_ENTRY(__cpp_lib_integer_comparison_functions)
    COMPILER_FEATURE_ENTRY(__cpp_lib_interpolate)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_constant_evaluated)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_layout_compatible)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_nothrow_convertible)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_pointer_interconvertible)
    COMPILER_FEATURE_ENTRY(__cpp_lib_jthread)
    COMPILER_FEATURE_ENTRY(__cpp_lib_latch)
    COMPILER_FEATURE_ENTRY(__cpp_lib_list_remove_return_type)
    COMPILER_FEATURE_ENTRY(__cpp_lib_math_constants)
    COMPILER_FEATURE_ENTRY(__cpp_lib_polymorphic_allocator)
    COMPILER_FEATURE_ENTRY(__cpp_lib_ranges)
    COMPILER_FEATURE_ENTRY(__cpp_lib_remove_cvref)
    COMPILER_FEATURE_ENTRY(__cpp_lib_semaphore)
    COMPILER_FEATURE_ENTRY(__cpp_lib_shared_ptr_arrays)
    COMPILER_FEATURE_ENTRY(__cpp_lib_shift)
    COMPILER_FEATURE_ENTRY(__cpp_lib_smart_ptr_for_overwrite)
    COMPILER_FEATURE_ENTRY(__cpp_lib_source_location)
    COMPILER_FEATURE_ENTRY(__cpp_lib_span)
    COMPILER_FEATURE_ENTRY(__cpp_lib_ssize)
    COMPILER_FEATURE_ENTRY(__cpp_lib_starts_ends_with)
    COMPILER_FEATURE_ENTRY(__cpp_lib_string_view)
    COMPILER_FEATURE_ENTRY(__cpp_lib_syncbuf)
    COMPILER_FEATURE_ENTRY(__cpp_lib_three_way_comparison)
    COMPILER_FEATURE_ENTRY(__cpp_lib_to_address)
    COMPILER_FEATURE_ENTRY(__cpp_lib_to_array)
    COMPILER_FEATURE_ENTRY(__cpp_lib_type_identity)
    COMPILER_FEATURE_ENTRY(__cpp_lib_unwrap_ref)
    };

    static CompilerFeature cxx23[] = {
    //< 继续填充
    COMPILER_FEATURE_ENTRY(__cpp_if_consteval)
    COMPILER_FEATURE_ENTRY(__cpp_size_t_suffix)
    };
    static CompilerFeature cxx23lib[] = {
    //< 继续填充
    COMPILER_FEATURE_ENTRY(__cpp_lib_constexpr_typeinfo)
    COMPILER_FEATURE_ENTRY(__cpp_lib_invoke_r)
    COMPILER_FEATURE_ENTRY(__cpp_lib_is_scoped_enum)
    COMPILER_FEATURE_ENTRY(__cpp_lib_stacktrace)
    COMPILER_FEATURE_ENTRY(__cpp_lib_stdatomic_h)
    COMPILER_FEATURE_ENTRY(__cpp_lib_string_contains)
    COMPILER_FEATURE_ENTRY(__cpp_lib_to_underlying)
    COMPILER_FEATURE_ENTRY(__cpp_lib_variant)
    };

    static CompilerFeature attributes[] = {
    COMPILER_ATTRIBUTE_ENTRY(carries_dependency)
    COMPILER_ATTRIBUTE_ENTRY(deprecated)
    COMPILER_ATTRIBUTE_ENTRY(fallthrough)
    COMPILER_ATTRIBUTE_ENTRY(likely)
    COMPILER_ATTRIBUTE_ENTRY(maybe_unused)
    COMPILER_ATTRIBUTE_ENTRY(nodiscard)
    COMPILER_ATTRIBUTE_ENTRY(noreturn)
    COMPILER_ATTRIBUTE_ENTRY(no_unique_address)
    COMPILER_ATTRIBUTE_ENTRY(unlikely)
    };

    constexpr bool is_feature_supported(const CompilerFeature& x) {
        return x.value[0] != '_' && x.value[0] != '0' ;
    }

    inline void print_compiler_feature(const CompilerFeature& x) {
        constexpr static int max_name_length = 44; //< Update if necessary
        std::string value{ is_feature_supported(x) ? x.value : "------" };
        if (value.back() == 'L') value.pop_back(); //~ 201603L -> 201603
        // value.insert(4, 1, '-'); //~ 201603 -> 2016-03
        if ( (print.supported_features && is_feature_supported(x))
            or (print.unsupported_features && !is_feature_supported(x))) {
                std::cout << std::left << std::setw(max_name_length)
                          << x.name << " " << value << '\n';
        }
    }

    template<std::size_t N>
    inline void show(char const* title, CompilerFeature (&features)[N]) {
        if (print.titles) {
            std::cout << '\n' << std::left << title << '\n';
        }
        if (print.sorted_by_value) {
            std::sort(std::begin(features), std::end(features),
                [](CompilerFeature const& lhs, CompilerFeature const& rhs) {
                    return std::strcmp(lhs.value, rhs.value) < 0;
                });
        }
        for (const CompilerFeature& x : features) {
            print_compiler_feature(x);
        }
    }

    int main() {
        if (print.general_features) show("C++ GENERAL", cxx);
        if (print.cxx11 && print.core_features) show("C++11 CORE", cxx11);
        if (print.cxx14 && print.core_features) show("C++14 CORE", cxx14);
        if (print.cxx14 && print.lib_features ) show("C++14 LIB" , cxx14lib);
        if (print.cxx17 && print.core_features) show("C++17 CORE", cxx17);
        if (print.cxx17 && print.lib_features ) show("C++17 LIB" , cxx17lib);
        if (print.cxx20 && print.core_features) show("C++20 CORE", cxx20);
        if (print.cxx20 && print.lib_features ) show("C++20 LIB" , cxx20lib);
        if (print.cxx23 && print.core_features) show("C++23 CORE", cxx23);
        if (print.cxx23 && print.lib_features ) show("C++23 LIB" , cxx23lib);
        if (print.attributes) show("ATTRIBUTES", attributes);
    }

可能的输出：

    C++ GENERAL
    __cplusplus                                  202002
    __cpp_exceptions                             199711
    __cpp_rtti                                   199711

    C++11 CORE
    __cpp_alias_templates                        200704
    __cpp_attributes                             200809
    __cpp_constexpr                              201907
    __cpp_decltype                               200707
    __cpp_delegating_constructors                200604
    __cpp_inheriting_constructors                201511
    __cpp_initializer_lists                      200806
    __cpp_lambdas                                200907
    __cpp_nsdmi                                  200809
    __cpp_range_based_for                        201603
    __cpp_raw_strings                            200710
    __cpp_ref_qualifiers                         200710
    __cpp_rvalue_references                      200610
    __cpp_static_assert                          201411
    __cpp_threadsafe_static_init                 200806
    __cpp_unicode_characters                     200704
    __cpp_unicode_literals                       200710
    __cpp_user_defined_literals                  200809
    __cpp_variadic_templates                     200704

    C++14 CORE
    __cpp_aggregate_nsdmi                        201304
    __cpp_binary_literals                        201304
    __cpp_constexpr                              201907
    __cpp_decltype_auto                          201304
    __cpp_generic_lambdas                        201707
    __cpp_init_captures                          201803
    __cpp_return_type_deduction                  201304
    __cpp_sized_deallocation                     ------
    __cpp_variable_templates                     201304

    ... truncated ...

### 参阅

- 库功能特性测试宏 (C++20) 定义于 `<version>`
- 特性测试推荐的官方文档
- 试出编译器特性的源码