C++20

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C++20是继C++17之后的一个重要版本，引入了主要特性（概念、模块、协程和范围）以及其他语言和库功能。该标准于2020年12月发布。

本节内容尚不完整

新语言特性

功能测试宏
三路比较运算符 <=> 与 operator == ( ) = default
指派初始化器
范围 for 循环中的初始化语句与初始化器
char8_t
新增属性： [[ no_unique_address ]] , [[ likely ]] , [[ unlikely ]]
包展开 在 lambda初始化捕获中的使用
移除了在许多上下文中使用 typename 消除类型歧义的要求
consteval , constinit
进一步放宽constexpr限制
有符号整数采用二进制补码表示
位运算移位操作符行为统一
使用圆括号进行聚合初始化
协程
模块
约束与概念
简写函数模板
DR11: 数组new表达式可推导数组大小

新库特性

新增头文件

在线程支持库中：

库功能特性

库特性测试宏
格式化库
概念库
日历与时区库（位于 <chrono> ）
std::source_location
std::span
std::endian ： big / little / native
二次幂整数运算及 std::bit_cast （位于 <bit> ）
std::make_shared 的数组支持
std::remove_cvref
std::to_address
浮点原子类型、 std::shared_ptr 原子操作
线程协调类： std::barrier 、 std::latch 与 std::counting_semaphore
std::jthread 及线程取消类： std::stop_token 、 std::stop_source 与 std::stop_callback
std::basic_osyncstream
std::basic_string 及其他 char8_t 应用
constexpr 支持（适用于 <algorithm> 、 <utility> 、 <complex> ）
string::starts_with / ends_with 及 string_view::starts_with / ends_with
std::assume_aligned
std::bind_front
std::c8rtomb / std::mbrtoc8
std::make_obj_using_allocator 等
std::make_shared_for_overwrite / std::make_unique_for_overwrite
无序关联容器的异构查找
std::pmr::polymorphic_allocator （含新增成员函数，默认模板参数为 std::byte ）
execution::unseq
std::midpoint 与 std::lerp
std::ssize
std::is_bounded_array 、 std::is_unbounded_array
范围库
统一容器擦除： std::erase / std::erase_if ，例如 std::erase(std::list) 或 erase_if(std::map) 等
数学常量（位于 <numbers> ）

缺陷报告

C++20 中已修复的缺陷报告（158 项核心，345 项库）
CWG#555 CWG#581 CWG#682 CWG#943 CWG#1076 CWG#1271 CWG#1299 CWG#1331 CWG#1332 CWG#1426 CWG#1469 CWG#1523 CWG#1581 CWG#1621 CWG#1632 CWG#1636 CWG#1640 CWG#1646 CWG#1704 CWG#1728 CWG#1781 CWG#1836 CWG#1857 CWG#1859 CWG#1862 CWG#1893 CWG#1910 CWG#1912 CWG#1913 CWG#1931 CWG#1937 CWG#1938 CWG#1943 CWG#1983 CWG#2020 CWG#2045 CWG#2051 CWG#2053 CWG#2059 CWG#2080 CWG#2081 CWG#2083 CWG#2088 CWG#2092 CWG#2103 CWG#2112 CWG#2126 CWG#2133 CWG#2164 CWG#2170 CWG#2177 CWG#2207 CWG#2226 CWG#2227 CWG#2229 CWG#2233 CWG#2234 CWG#2235 CWG#2237 CWG#2241 CWG#2249 CWG#2253 CWG#2254 CWG#2255 CWG#2256 CWG#2257 CWG#2260 CWG#2266 CWG#2267 CWG#2273 CWG#2277 CWG#2278 CWG#2280 CWG#2282 CWG#2285 CWG#2287 CWG#2289 CWG#2290 CWG#2292 CWG#2293 CWG#2294 CWG#2295 CWG#2299 CWG#2300 CWG#2303 CWG#2305 CWG#2307 CWG#2309 <a class="external text" href="https://wg21.cmeerw.net/cwg/issue2310" rel="nofollow

C++20 中已修复的缺陷报告（158 项核心，345 项库）

CWG#555
CWG#581
CWG#682
CWG#943
CWG#1076
CWG#1271
CWG#1299
CWG#1331
CWG#1332
CWG#1426
CWG#1469
CWG#1523
CWG#1581
CWG#1621
CWG#1632
CWG#1636
CWG#1640
CWG#1646
CWG#1704
CWG#1728
CWG#1781
CWG#1836
CWG#1857
CWG#1859
CWG#1862
CWG#1893
CWG#1910
CWG#1912
CWG#1913
CWG#1931
CWG#1937
CWG#1938
CWG#1943
CWG#1983
CWG#2020
CWG#2045
CWG#2051
CWG#2053
CWG#2059
CWG#2080
CWG#2081
CWG#2083
CWG#2088
CWG#2092
CWG#2103
CWG#2112
CWG#2126
CWG#2133
CWG#2164
CWG#2170
CWG#2177
CWG#2207
CWG#2226
CWG#2227
CWG#2229
CWG#2233
CWG#2234
CWG#2235
CWG#2237
CWG#2241
CWG#2249
CWG#2253
CWG#2254
CWG#2255
CWG#2256
CWG#2257
CWG#2260
CWG#2266
CWG#2267
CWG#2273
CWG#2277
CWG#2278
CWG#2280
CWG#2282
CWG#2285
CWG#2287
CWG#2289
CWG#2290
CWG#2292
CWG#2293
CWG#2294
CWG#2295
CWG#2299
CWG#2300
CWG#2303
CWG#2305
CWG#2307
CWG#2309
<a class="external text" href="https://wg21.cmeerw.net/cwg/issue2310" rel="nofollow

编译器支持

主条目： C++20 编译器支持

C++20 核心语言特性

C++20 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	Nvidia HPC C++ (ex PGI)*	Nvidia nvcc	Cray
Allow Lambda capture [ = , this ]	P0409R2	8	6	19.22*	10.0.0*	5.1	2021.1	20.7	12.0	11.0
`__VA_OPT__`	P0306R4 P1042R1	8 (partial)* 10 (partial)* 12	9	19.25*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Designated initializers ( FTM ) *	P0329R4	4.7 (partial)* 8	3.0 (partial)* 10	19.21*	12.0.0*	5.1	2021.1	20.7	12.0	11.0
template-parameter-list for generic lambdas ( FTM ) *	P0428R2	8	9	19.22*	11.0.0*	5.1	2021.1	20.7	12.0	11.0
Default member initializers for bit-fields	P0683R1	8	6	19.25*	10.0.0*	5.1	2021.1	20.7	12.0	11.0
Initializer list constructors in class template argument deduction	P0702R1	8	6	19.14*	Yes	5.0	2021.1	20.7	12.0	11.0
const & -qualified pointers to members	P0704R1	8	6	19.0 (2015)*	10.0.0*	5.1	2021.1	20.7	12.0	11.0
Concepts ( FTM ) *	P0734R0	5* 10	10	19.23* (partial)* 19.30*	12.0.0* (partial)	6.1	2023.1*	20.11	12.0	11.0
Lambdas in unevaluated contexts	P0315R4	9	13 (partial)* 14 (partial)* 17	19.28 (16.8)*	13.1.6* (partial)	6.2	2023.1 (partial) 2024.0	20.7	12.0
Three-way comparison operator ( FTM ) *	P0515R3	10	8 (partial) 10	19.20*	12.0.0*	5.1	2021.1	20.7	12.0	11.0
DR11: Simplifying implicit lambda capture	P0588R1	8		19.24*		5.1	2021.1	20.7	12.0
init-statements for range-based for	P0614R1	9	8	19.25*	11.0.0*	6.0	2021.7	20.11	12.0	11.0
Default constructible and assignable stateless lambdas	P0624R2	9	8	19.22*	10.0.1*	5.1	2021.1	20.7	12.0	11.0
Type mismatch of defaulted special member functions	P0641R2	9 (partial)*	8	19.0 (2015)* (partial)*	10.0.1*	5.1	2021.1	20.7	12.0	11.0
Access checking on specializations	P0692R1	Yes	8 (partial) 14	19.26*	14.0.0*	5.1	2021.1	20.7	12.0
ADL and function templates that are not visible	P0846R0	9	9	19.21*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
DR11: Specify when constexpr function definitions are needed for constant evaluation ( FTM ) *	P0859R0	5.2 (partial)* 9	8	19.27* (partial)* 19.31* *	11.0.0*	(partial)			12.0	11.0
Attributes `[[ likely ]]` and `[[ unlikely ]]`	P0479R5	9	12	19.26*	13.0.0*	5.1	2021.7	20.7	12.0
Make `typename` more optional	P0634R3	9	16	19.29 (16.10)*	16.0.0*	5.1	2023.1	20.7	12.0
`Pack-expansions` in lambda init-captures ( FTM ) *	P0780R2	9	9	19.22*	11.0.3*	6.1	2021.7	20.11	12.0	11.0
Attribute `[[ no_unique_address ]]`	P0840R2	9	9	19.28 (16.9)* *	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Conditionally trivial special member functions ( FTM ) *	P0848R3	10	16	19.28 (16.8)*		6.1	2021.7	20.11	12.0
DR17: Relaxing the structured bindings customization point finding rules	P0961R1	8	8	19.20*	10.0.1*	5.1	2021.1	20.7	12.0	11.0
DR11: Relaxing the range-for loop customization point finding rules	P0962R1	8	8	19.25*	11.0.0*	5.1	2021.1	20.7	12.0	11.0
DR17: Allow structured bindings to accessible members	P0969R0	8	8	19.20*	10.0.1*	5.1	2021.1	20.7	12.0	11.0
Destroying `operator delete` ( FTM ) *	P0722R3	9	6	19.27*	10.0.0*	6.1	2023.1	20.11	12.0	11.0
Class types in Constant template parameters	P0732R2	9	12 (partial)	19.26* (partial)* 19.28 (16.9)*	13.0.0* (partial)	6.2	2023.1 (partial)	21.3	12.0
Deprecate implicit capture of this via `[=]`	P0806R2	9	7	19.22*	10.0.1*	5.1		20.7	12.0	11.0
`explicit(bool)` ( FTM ) *	P0892R2	9	9	19.24*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Integrating feature-test macros	P0941R2	5	3.4	19.15* (partial) 19.20*	Yes	5.0	2021.1	20.7	12.0	11.0
Prohibit aggregates with user-declared constructors	P1008R1	9	8	19.20*	10.0.1*	5.1	2021.1	20.7	12.0	11.0
constexpr virtual function ( FTM ) *	P1064R0	9	9	19.28 (16.9)*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Consistency improvements for comparisons	P1120R0	10	8 (partial) 10	19.22*	12.0.0*	5.1	2023.1	20.7	12.0	11.0
`char8_t` ( FTM ) *	P0482R6	9	7*	19.22*	10.0.0*	5.1	2021.1	20.7	12.0	11.0
`std::is_constant_evaluated()` ( FTM ) *	P0595R2	9	9	19.25*	11.0.3*	5.1	19.1	21.1	12.0	11.0
constexpr try - catch blocks	P1002R1	9	8	19.25*	10.0.1*	5.1	2023.1	20.7	12.0	11.0
Immediate functions ( consteval ) ( FTM ) *	P1073R3	10 (partial)* 11	11 (partial) 14 (partial)* 17	19.28 (16.8)* (partial)* 19.29 (16.10)*	11.0.3* (partial) 15.0.0*	5.1	2021.1	20.7	12.0
Nested inline namespaces	P1094R2	9	8	19.27*	10.0.1*	5.1	2021.1	20.7	12.0	11.0
Yet another approach for constrained declarations	P1141R2	10	10	19.26* (partial) 19.28 (16.9)*	12.0.5*	6.1	2023.1	20.11	12.0	11.0
Signed integers are two's complement	P1236R1	9	9	Yes	11.0.3*	N/A	2023.1*	yes*	12.0	11.0
`dynamic_cast` and polymorphic `typeid` in constant expressions	P1327R1	10	9	19.28 (16.9)*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Changing the active member of a union inside constexpr ( FTM ) *	P1330R0	9	9	19.10*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Coroutines ( FTM ) * ( FTM ) *	P0912R5 LWG3393	10	8 (partial) 17 (partial)*	19.0 (2015)* (partial) 19.10* * 19.28 (16.8)*	10.0.1* (partial)	5.1	2021.1	23.3*	12.0 (host code only)
Parenthesized initialization of aggregates ( FTM ) *	P0960R3	10	16	19.28 (16.8)*	16.0.0*	5.1	2021.1	20.7	12.0
DR11: Array size deduction in `new` -expressions	P1009R2	11	9	19.27*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Modules ( FTM ) *	P1103R3	11 (partial)	8 (partial)	19.0 (2015)* (partial) 19.10* * 19.28 (16.8)*	10.0.1* (partial)		2023.1 (partial)
Stronger Unicode requirements	P1041R4 P1139R2	10	Yes	19.0 (2015)* * 19.26* *	Yes	N/A	2023.1*	Yes	12.0	11.0
`<=> != ==`	P1185R2	10	10	19.22*	12.0.0*	5.1	2021.1	20.7	12.0	11.0
DR11: Explicitly defaulted functions with different exception specifications	P1286R2	10	9	19.28 (16.8)*	11.0.3*	5.1	2021.1	20.7	12.0	11.0
Lambda capture and storage class specifiers of structured bindings	P1091R3 P1381R1	10	8 (partial) 16	19.11* * 19.24* *	16.0.0*	5.1	2021.1	20.7	12.0
Permit conversions to arrays of unknown bound	P0388R4	10	14	19.27*	14.0.0*	6.0	2021.5	20.11	12.0
constexpr container operations ( FTM ) *	P0784R7	10	10	19.28 (16.9)*	12.0.0*	6.0	2021.5	20.11	12.0	11.0
Deprecating some uses of `volatile`	P1152R4	10	10	19.27*	12.0.0*	6.0	2021.5	20.11	12.0	11.0
`constinit` ( FTM ) *	P1143R2	10	10	19.29 (16.10)*	12.0.0*	6.1	2021.7	20.11	12.0	11.0
Deprecate comma operator in subscripts	P1161R3	10	9	19.25*	11.0.3*	6.0	2021.7	20.11	12.0	11.0
`[[ nodiscard ]]` with message	P1301R4	10	9	19.25*	11.0.3*	6.0	2021.5	20.11	12.0	11.0
Trivial default initialization in constexpr functions	P1331R2	10	10	19.27*	12.0.0*	6.1	2021.7	20.11	12.0	11.0
Unevaluated asm -declaration in constexpr functions	P1668R1	10	10	19.28 (16.9)*	12.0.0*	6.1	2021.7	20.11	12.0	11.0
`using enum` ( FTM ) *	P1099R5	11	13	19.24*	13.1.6*	6.3	2023.1	22.5	12.0
Synthesizing Three-way comparison for specified comparison category	P1186R3	11	10	19.24*	12.0.0*	6.0	2021.5	20.11	12.0	11.0
DR17: `[[ nodiscard ]]` for constructors	P1771R1	10	9	19.24*	11.0.3*	6.0	2021.5	20.11	12.0	11.0
class template argument deduction for alias templates ( FTM ) *	P1814R0	10	19	19.27*		6.5		23.9	12.0
class template argument deduction for aggregates ( FTM ) *	P1816R0 P2082R1	10* 11*	17	19.27*		6.3	2023.1 (partial)* 2024.1	23.3	12.0
DR11: Implicit move for more local objects and rvalue references	P1825R0	11*	13	19.24*	13.1.6*	6.0	2021.5	20.11	12.0
Allow defaulting comparisons by value	P1946R0	10	10	19.25*	12.0.0*	6.1	2021.7	20.11	12.0	11.0
Remove `std::weak_equality` and `std::strong_equality`	P1959R0	10	10	19.25*	12.0.0*	6.1	2021.7	20.11	12.0	11.0
Inconsistencies with constant template parameters ( FTM ) *	P1907R1	10 (partial) 11	18 (partial)*	19.26*	13.1.6* (partial)	6.2	2023.1 (partial)	21.3	12.0
DR98: Pseudo-destructors end object lifetimes	P0593R6	11	11	Yes	12.0.5*	N/A	2023.1*	Yes	12.0	11.0
DR11: Converting from T * to bool should be considered narrowing	P1957R2	10* 11*	11	19.27*	12.0.5*	6.1			12.0	11.0
C++20 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	Nvidia HPC C++ (ex PGI)*	Nvidia nvcc	Cray

C++20 标准库特性

C++20 feature	Paper(s)	GCC libstdc++	Clang libc++	MSVC STL	Apple Clang*
`std::endian` ( FTM ) *	P0463R1	8	7	19.22*	10.0.0*
Extending std::make_shared() to support arrays ( FTM ) *	P0674R1	12	15	19.27*	14.0.3*
Floating-point atomic ( FTM ) *	P0020R6	10	18	19.22*	16.0.0*
Synchronized buffered ( `std::basic_osyncstream` ) ( FTM ) *	P0053R7	11	18	19.29 (16.10)*
constexpr for `<algorithm>` and `<utility>` ( FTM ) *	P0202R3	10	8 (partial) 12	19.26*	10.0.1* (partial) 13.0.0*
More constexpr for `<complex>` ( FTM ) *	P0415R1	9	7 (partial) 16	19.27*	10.0.0* (partial) 15.0.0*
Make std::memory_order a scoped enumeration	P0439R0	9	9	19.25*	11.0.3*
String prefix and suffix checking: `string` `(_view)` `::starts_with` / `ends_with` ( FTM ) *	P0457R2	9	6	19.21*	10.0.0*
Library support for `operator<=>` `<compare>` ( FTM ) *	P0768R1	10	7 (partial) 12 (partial)* 17	19.20* (partial) 19.28 (16.9)*	13.0.0*
`std::remove_cvref` ( FTM ) *	P0550R2	9	6	19.20*	10.0.0*
`[[ nodiscard ]]` in the standard library	P0600R1	9	7 (partial) 16	19.13* (partial) 19.22*	10.0.0* (partial) 15.0.0*
Using `std::move` in numeric algorithms	P0616R0	9	12	19.23*	13.0.0*
Utility to convert a pointer to a raw pointer ( FTM ) *	P0653R2	8	6	19.22*	Yes
Atomic `std::shared_ptr` and `std::weak_ptr` ( FTM ) *	P0718R2	12		19.27*
`std::span` ( FTM ) *	P0122R7	10	7	19.26*	10.0.0*
Calendar and Time zone ( FTM ) *	P0355R7	11 (partial)* 13 (partial)* 14	7 (partial) 19 ( partial )*	19.29 (16.10)*	10.0.0* (partial)
`<version>`	P0754R2	9	7	19.22*	10.0.0*
Comparing unordered containers	P0809R0	Yes	Yes	16.0*	Yes
ConstexprIterator requirements ( FTM ) * ( FTM ) *	P0858R0	9	12	19.11*	13.0.0*
std::basic_string::reserve() should not shrink	P0966R1	11	8	19.25*	10.0.1*
Atomic Compare-And-Exchange with padding bits	P0528R3	13		19.28 (16.8)*
`std::atomic_ref` ( FTM ) *	P0019R8	10	19	19.28 (16.8)*
contains ( ) member function of associative containers, e.g. `std::map::contains()`	P0458R2	9	13	19.21*	13.1.6*
DR11: Guaranteed copy elision for piecewise construction	P0475R1	9	Yes	19.29 (16.10)*	Yes
`std::bit_cast()` ( FTM ) *	P0476R2	11	14	19.27*	14.0.3*
Integral power-of- $2$ operations : `std::bit_ceil()` , `std::bit_floor()` , `std::bit_width()` , `std::has_single_bit()` ( FTM ) *	P0556R3 P1956R1	9* 10*	9* 12*	19.25* * 19.27* * 19.28 (16.8)*	11.0.3* * 13.0.0* *
Improving the return value of erase-like algorithms ( FTM ) *	P0646R1	9	10	19.21*	12.0.0*
`std::destroying_delete_t` ( FTM ) *	P0722R3	9	9	19.27*	11.0.3*
`std::is_convertible` ( FTM ) *	P0758R1	9	9	19.23*	11.0.3*
Add `std::shift_left/right` to `<algorithm>` ( FTM ) *	P0769R2	10	12	19.21*	13.0.0*
Constexpr for std::swap() and `swap` related functions	P0879R0	10	13	19.26*	13.1.6*
`std::type_identity` ( FTM ) *	P0887R1	9	8	19.21*	10.0.1*
Concepts library ( FTM ) *	P0898R3	10	13	19.23*	13.1.6*
`constexpr` comparison operators for std::array	P1023R0	10	8	19.27*	10.0.1*
`std::unwrap_ref_decay` and `std::unwrap_reference` ( FTM ) *	P0318R1	9	8	19.21*	10.0.1*
`std::bind_front()` ( FTM ) *	P0356R5	9	13	19.25*	13.1.6*
std::reference_wrapper for incomplete types	P0357R3	9	8	19.26*	10.0.1*
Fixing `operator>>(basic_istream&, CharT*)`	P0487R1	11	8	19.23*	10.0.1*
Library support for `char8_t` ( FTM ) *	P0482R6	9	8 (partial) 16	19.22*	10.0.1* (partial) 15.0.0*
Utility functions to implement uses-allocator construction	P0591R4	9	16	19.29 (16.10)*	15.0.0*
DR17: std::variant and std::optional should propagate copy/move triviality	P0602R4	8.3	8	19.11*	10.0.1*
DR17: A sane std::variant converting constructor	P0608R3	10	9	19.29 (16.10)* * 19.42* *	11.0.3*
std::function 's move constructor should be `noexcept`	P0771R1	7.2	6	19.22*	Yes
The One Ranges Proposal ( FTM ) *	P0896R4	10	13 (partial) 15*	19.29 (16.10)*	14.0.3*
Heterogeneous lookup for unordered associative containers ( FTM ) *	P0919R3 P1690R1	11	12	19.23* (P0919R3) 19.25* (P1690R1)	13.0.0*
`<chrono>` `zero()` , `min()` , and `max()` should be `noexcept`	P0972R0	9	8	19.14*	10.0.1*
constexpr in std::pointer_traits ( FTM ) *	P1006R1	9	8	19.26*	10.0.1*
`std::assume_aligned()` ( FTM ) *	P1007R3	9* 11	15	19.28 (16.9)*	14.0.3*
Smart pointer creation with default initialization (e.g. `make_unique_for_overwrite` ) ( FTM ) *	P1020R1 P1973R1	11* 12*	16	19.28 (16.9)*	15.0.0*
Misc constexpr bits ( FTM ) * ( FTM ) * ( FTM ) * ( FTM ) * ( FTM ) * ( FTM ) *	P1032R1	10	13	19.28 (16.8)*	13.1.6*
Remove comparison operators of `std::span`	P1085R2	10	8	19.26*	10.0.1*
Make stateful allocator propagation more consistent for `operator+(basic_string)`	P1165R1	10	15	19.26*	14.0.3*
Consistent container erasure, e.g. `std::erase(std::vector)` , or `std::erase_if(std::map)` ( FTM ) *	P1209R0 P1115R3	9* 10*	8* 11*	19.25* * 19.27* *	10.0.1* * 12.0.5* *
Standard library header units	P1502R1	11		19.29 (16.10)*
`polymorphic_allocator<>` as a vocabulary type ( FTM ) *	P0339R6	9	16	19.28 (16.9)*	15.0.0*
`std::execution::unseq` ( FTM ) *	P1001R2	9	17	19.28 (16.8)*
`std::lerp()` and `std::midpoint()` ( FTM ) *	P0811R3	9	9	19.23* (partial) 19.28 (16.8)*	11.0.3*
Usability enhancements for `std::span`	P1024R3	10	9* 14	19.26*	11.0.3*
DR17: Make `std::create_directory()` intuitive	P1164R1	8.3	12	19.20*	13.0.0*
`std::ssize()` and unsigned extent for `std::span` ( FTM ) *	P1227R2	10	9	19.25*	11.0.3*
Traits for ( un ) bounded arrays ( FTM ) *	P1357R1	9	9	19.25*	11.0.3*
`std::to_array()` ( FTM ) *	P0325R4	10	10	19.25*	12.0.0*
Efficient access to std::basic_stringbuf ’s buffer	P0408R7	11	17	19.29 (16.10)*	15.0.0*
Layout - compatibility and pointer - interconvertibility traits ( FTM ) * ( FTM ) *	P0466R5	12		19.29 (16.10)* *
Bit operations : std :: `rotl()` , `rotr()` , `countl_zero()` , `countl_one()` , `countr_zero()` , `countr_one()` , `popcount()` ( FTM ) *	P0553R4	9	9	19.25* * 19.28 (16.8)*	11.0.3*
Mathematical constants ( FTM ) *	P0631R8	10	11	19.25*	12.0.5*
Text formatting ( FTM ) *	P0645R10	13	14 * * 17	19.29 (16.10)*	15.0.0*
`std::stop_token` and `std::jthread` ( FTM ) *	P0660R10	10	17 (partial)* 20*	19.28 (16.9)*
constexpr std::allocator and related utilities ( FTM ) *	P0784R7	10	12	19.29 (16.10)*	13.0.0*
constexpr std::string ( FTM ) *	P0426R1 P1032R1 P0980R1	12	15	19.29 (16.10)* 19.30* *	14.0.3*
constexpr std::vector ( FTM ) *	P1004R2	12	15	19.29 (16.10)* 19.30* *	14.0.3*
Input range adaptors	P1035R7	10	16	19.29 (16.10)*	15.0.0*
constexpr std::invoke() and related utilities	P1065R2	10	12	19.28 (16.8)*	13.0.0*
Atomic waiting and notifying, `std::counting_semaphore` , `std::latch` and `std::barrier` ( FTM ) * ( FTM ) * ( FTM ) * ( FTM ) * ( FTM ) * ( FTM ) *	P1135R6	11	11	19.28 (16.9)*	13.1.6*
`std::source_location` ( FTM ) *	P1208R6	11	15* (partial) 16	19.29 (16.10)*	15.0.0*
Adding `<=>` to the standard library	P1614R2	10	14* (partial) 17* (partial) 19	19.29 (16.10)*	13.1.6* (partial)
constexpr default constructor of std::atomic and std::atomic_flag ( FTM ) *	P0883R2	10	13	19.26*	13.1.6*
constexpr for numeric algorithms ( FTM ) *	P1645R1	10	12	19.26*	13.0.0*
Safe integral comparisons ( FTM ) *	P0586R2	10	13	19.27*	13.1.6*
C++20 feature	Paper(s)	GCC libstdc++	Clang libc++	MSVC STL	Apple Clang*

* - 将鼠标悬停在带有星号 * 的单元格上可查看附加弹窗注释。
DR nn - "DR" 后的数字 nn 表示缺陷报告所适用的目标 C++ 修订版本，例如 DR20 → C++20。

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1.	C++20 - 维基百科
2.	可运行的C++20示例

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