libc++ C++20 Status

Overview

In July 2017, the C++ standard committee created a draft for the next version of the C++ standard, initially known as “C++2a”. In September 2020, the C++ standard committee approved this draft, and sent it to ISO for approval as C++20.

This page shows the status of libc++; the status of clang’s support of the language features is here.

Attention

Features in unreleased drafts of the standard are subject to change.

The groups that have contributed papers:

• CWG - Core Language Working group

• LWG - Library working group

• SG1 - Study group #1 (Concurrency working group)

Note

“Nothing to do” means that no library changes were needed to implement this change.

Paper Status

Paper #	Group	Paper Name	Meeting	Status	First released version
P0463R1	LWG	Endian just Endian	Toronto	Complete	7.0
P0674R1	LWG	Extending make_shared to Support Arrays	Toronto
P0020R6	LWG	Floating Point Atomic	Albuquerque
P0053R7	LWG	C++ Synchronized Buffered Ostream	Albuquerque
P0202R3	LWG	Add constexpr modifiers to functions in <algorithm> and <utility> Headers	Albuquerque	Complete	12.0
P0415R1	LWG	Constexpr for std::complex	Albuquerque	In Progress	7.0
P0439R0	LWG	Make std::memory_order a scoped enumeration	Albuquerque	Complete
P0457R2	LWG	String Prefix and Suffix Checking	Albuquerque	Complete	6.0
P0550R2	LWG	Transformation Trait remove_cvref	Albuquerque	Complete	6.0
P0600R1	LWG	nodiscard in the Library	Albuquerque	In Progress 1	7.0
P0616R0	LWG	de-pessimize legacy <numeric> algorithms with std::move	Albuquerque	Complete	12.0
P0653R2	LWG	Utility to convert a pointer to a raw pointer	Albuquerque	Complete	6.0
P0718R2	LWG	Atomic shared_ptr	Albuquerque
P0767R1	CWG	Deprecate POD	Albuquerque	Complete	7.0
P0768R1	CWG	Library Support for the Spaceship (Comparison) Operator	Albuquerque	Complete
P0777R1	LWG	Treating Unnecessary decay	Albuquerque	Complete	7.0
P0122R7	LWG	<span>	Jacksonville	Complete	7.0
P0355R7	LWG	Extending chrono to Calendars and Time Zones	Jacksonville	In Progress
P0551R3	LWG	Thou Shalt Not Specialize std Function Templates!	Jacksonville	Complete	11.0
P0753R2	LWG	Manipulators for C++ Synchronized Buffered Ostream	Jacksonville
P0754R2	LWG	<version>	Jacksonville	Complete	7.0
P0809R0	LWG	Comparing Unordered Containers	Jacksonville	Nothing To Do
P0858R0	LWG	Constexpr iterator requirements	Jacksonville
P0905R1	CWG	Symmetry for spaceship	Jacksonville
P0966R1	LWG	string::reserve Should Not Shrink	Jacksonville	Complete 2	12.0
P0019R8	LWG	Atomic Ref	Rapperswil
P0458R2	LWG	Checking for Existence of an Element in Associative Containers	Rapperswil	Complete
P0475R1	LWG	LWG 2511: guaranteed copy elision for piecewise construction	Rapperswil	Complete
P0476R2	LWG	Bit-casting object representations	Rapperswil
P0528R3	CWG	The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange	Rapperswil
P0542R5	CWG	Support for contract based programming in C++	Rapperswil	Removed in Cologne	n/a
P0556R3	LWG	Integral power-of-2 operations	Rapperswil	Complete	9.0
P0619R4	LWG	Reviewing Deprecated Facilities of C++17 for C++20	Rapperswil	Partial 3
P0646R1	LWG	Improving the Return Value of Erase-Like Algorithms	Rapperswil	Complete	10.0
P0722R3	CWG	Efficient sized delete for variable sized classes	Rapperswil	Complete	9.0
P0758R1	LWG	Implicit conversion traits and utility functions	Rapperswil	Complete
P0759R1	LWG	fpos Requirements	Rapperswil	Complete	11.0
P0769R2	LWG	Add shift to <algorithm>	Rapperswil	Complete	12.0
P0788R3	LWG	Standard Library Specification in a Concepts and Contracts World	Rapperswil	Removed in Cologne	n/a
P0879R0	LWG	Constexpr for swap and swap related functions Also resolves LWG issue 2800.	Rapperswil
P0887R1	LWG	The identity metafunction	Rapperswil	Complete	8.0
P0892R2	CWG	explicit(bool)	Rapperswil
P0898R3	LWG	Standard Library Concepts	Rapperswil	In Progress
P0935R0	LWG	Eradicating unnecessarily explicit default constructors from the standard library	Rapperswil	Complete	12.0
P0941R2	CWG	Integrating feature-test macros into the C++ WD	Rapperswil	In Progress
P1023R0	LWG	constexpr comparison operators for std::array	Rapperswil	Complete	8.0
P1025R1	CWG	Update The Reference To The Unicode Standard	Rapperswil
P1120R0	CWG	Consistency improvements for <=> and other comparison operators	Rapperswil
P0318R1	LWG	unwrap_ref_decay and unwrap_reference	San Diego	Complete	8.0
P0356R5	LWG	Simplified partial function application	San Diego
P0357R3	LWG	reference_wrapper for incomplete types	San Diego	Complete	8.0
P0482R6	CWG	char8_t: A type for UTF-8 characters and strings	San Diego	In Progress
P0487R1	LWG	Fixing operator>>(basic_istream&, CharT*) (LWG 2499)	San Diego	Complete	8.0
P0591R4	LWG	Utility functions to implement uses-allocator construction	San Diego
P0595R2	CWG	P0595R2 std::is_constant_evaluated()	San Diego	Complete	9.0
P0602R4	LWG	variant and optional should propagate copy/move triviality	San Diego	Complete	8.0
P0608R3	LWG	A sane variant converting constructor	San Diego	Complete	9.0
P0655R1	LWG	visit<R>: Explicit Return Type for visit	San Diego	Complete	12.0
P0771R1	LWG	std::function move constructor should be noexcept	San Diego	Complete	6.0
P0896R4	LWG	The One Ranges Proposal	San Diego
P0899R1	LWG	P0899R1 - LWG 3016 is not a defect	San Diego	Nothing To Do
P0919R3	LWG	Heterogeneous lookup for unordered containers	San Diego	Complete	12.0
P0972R0	LWG	<chrono> zero(), min(), and max() should be noexcept	San Diego	Complete	8.0
P1006R1	LWG	Constexpr in std::pointer_traits	San Diego	Complete	8.0
P1007R3	LWG	std::assume_aligned	San Diego
P1020R1	LWG	Smart pointer creation with default initialization	San Diego
P1032R1	LWG	Misc constexpr bits	San Diego
P1085R2	LWG	Should Span be Regular?	San Diego	Complete	8.0
P1123R0	LWG	Editorial Guidance for merging P0019r8 and P0528r3	San Diego
P1148R0	LWG	Cleaning up Clause 20	San Diego
P1165R1	LWG	Make stateful allocator propagation more consistent for operator+(basic_string)	San Diego
P1209R0	LWG	Adopt Consistent Container Erasure from Library Fundamentals 2 for C++20	San Diego	Complete	8.0
P1210R0	LWG	Completing the Rebase of Library Fundamentals, Version 3, Working Draft	San Diego
P1236R1	CWG	Alternative Wording for P0907R4 Signed Integers are Two’s Complement	San Diego
P1248R1	LWG	Remove CommonReference requirement from StrictWeakOrdering (a.k.a Fixing Relations)	San Diego
P1285R0	LWG	Improving Completeness Requirements for Type Traits	San Diego
P1353R0	CWG	Missing feature test macros	San Diego
P0339R6	LWG	polymorphic_allocator<> as a vocabulary type	Kona
P0340R3	LWG	Making std::underlying_type SFINAE-friendly	Kona	Complete	9.0
P0738R2	LWG	I Stream, You Stream, We All Stream for istream_iterator	Kona
P0811R3	LWG	Well-behaved interpolation for numbers and pointers	Kona	Complete	9.0
P0920R2	LWG	Precalculated hash values in lookup	Kona	Reverted by P1661
P1001R2	LWG	Target Vectorization Policies from Parallelism V2 TS to C++20	Kona
P1024R3	LWG	Usability Enhancements for std::span	Kona	Complete	9.0
P1164R1	LWG	Make create_directory() Intuitive	Kona	Complete	12.0
P1227R2	LWG	Signed ssize() functions, unsigned size() functions	Kona	Complete	9.0
P1252R2	LWG	Ranges Design Cleanup	Kona
P1286R2	CWG	Contra CWG DR1778	Kona
P1357R1	LWG	Traits for [Un]bounded Arrays	Kona	Complete	9.0
P1458R1	LWG	Mandating the Standard Library: Clause 16 - Language support library	Kona	Complete	9.0
P1459R1	LWG	Mandating the Standard Library: Clause 18 - Diagnostics library	Kona	Complete	9.0
P1462R1	LWG	Mandating the Standard Library: Clause 20 - Strings library	Kona	Complete	9.0
P1463R1	LWG	Mandating the Standard Library: Clause 21 - Containers library	Kona
P1464R1	LWG	Mandating the Standard Library: Clause 22 - Iterators library	Kona	Complete	9.0
P0325	LWG	to_array from LFTS with updates	Cologne	Complete	10.0
P0408	LWG	Efficient Access to basic_stringbuf’s Buffer	Cologne
P0466	LWG	Layout-compatibility and Pointer-interconvertibility Traits	Cologne
P0553	LWG	Bit operations	Cologne	Complete	9.0
P0631	LWG	Math Constants	Cologne	Complete	11.0
P0645	LWG	Text Formatting	Cologne
P0660	LWG	Stop Token and Joining Thread, Rev 10	Cologne
P0784	CWG	More constexpr containers	Cologne	Complete	12.0
P0980	LWG	Making std::string constexpr	Cologne
P1004	LWG	Making std::vector constexpr	Cologne
P1035	LWG	Input Range Adaptors	Cologne
P1065	LWG	Constexpr INVOKE	Cologne	Complete	12.0
P1135	LWG	The C++20 Synchronization Library	Cologne	Complete	11.0
P1207	LWG	Movability of Single-pass Iterators	Cologne
P1208	LWG	Adopt source_location for C++20	Cologne
P1355	LWG	Exposing a narrow contract for ceil2	Cologne	Complete	9.0
P1361	LWG	Integration of chrono with text formatting	Cologne
P1423	LWG	char8_t backward compatibility remediation	Cologne	In Progress
P1424	LWG	‘constexpr’ feature macro concerns	Cologne	Superseded by P1902
P1466	LWG	Miscellaneous minor fixes for chrono	Cologne
P1474	LWG	Helpful pointers for ContiguousIterator	Cologne
P1502	LWG	Standard library header units for C++20	Cologne
P1522	LWG	Iterator Difference Type and Integer Overflow	Cologne
P1523	LWG	Views and Size Types	Cologne
P1612	LWG	Relocate Endian’s Specification	Cologne	Complete	10.0
P1614	LWG	The Mothership has Landed	Cologne	In Progress
P1638	LWG	basic_istream_view::iterator should not be copyable	Cologne
P1643	LWG	Add wait/notify to atomic_ref	Cologne
P1644	LWG	Add wait/notify to atomic<shared_ptr>	Cologne
P1650	LWG	Output std::chrono::days with ‘d’ suffix	Cologne
P1651	LWG	bind_front should not unwrap reference_wrapper	Cologne
P1652	LWG	Printf corner cases in std::format	Cologne
P1661	LWG	Remove dedicated precalculated hash lookup interface	Cologne	Nothing To Do
P1754	LWG	Rename concepts to standard_case for C++20, while we still can	Cologne	In Progress
P0883	LWG	Fixing Atomic Initialization	Belfast
P1391	LWG	Range constructor for std::string_view	Belfast
P1394	LWG	Range constructor for std::span	Belfast
P1456	LWG	Move-only views	Belfast
P1622	LWG	Mandating the Standard Library: Clause 32 - Thread support library	Belfast
P1645	LWG	constexpr for numeric algorithms	Belfast	Complete	12.0
P1664	LWG	reconstructible_range - a concept for putting ranges back together	Belfast
P1686	LWG	Mandating the Standard Library: Clause 27 - Time library	Belfast
P1690	LWG	Refinement Proposal for P0919 Heterogeneous lookup for unordered containers	Belfast	Complete	12.0
P1716	LWG	ranges compare algorithm are over-constrained	Belfast
P1718	LWG	Mandating the Standard Library: Clause 25 - Algorithms library	Belfast
P1719	LWG	Mandating the Standard Library: Clause 26 - Numerics library	Belfast
P1720	LWG	Mandating the Standard Library: Clause 28 - Localization library	Belfast
P1721	LWG	Mandating the Standard Library: Clause 29 - Input/Output library	Belfast
P1722	LWG	Mandating the Standard Library: Clause 30 - Regular Expression library	Belfast
P1723	LWG	Mandating the Standard Library: Clause 31 - Atomics library	Belfast
P1855	LWG	Make <compare> freestanding	Belfast
P1862	LWG	Ranges adaptors for non-copyable iterators	Belfast
P1865	LWG	Add max() to latch and barrier	Belfast	Complete	11.0
P1869	LWG	Rename ‘condition_variable_any’ interruptible wait methods	Belfast
P1870	LWG	forwarding-range is too subtle	Belfast
P1871	LWG	Should concepts be enabled or disabled?	Belfast
P1872	LWG	span should have size_type, not index_type	Belfast	Complete	10.0
P1878	LWG	Constraining Readable Types	Belfast
P1892	LWG	Extended locale-specific presentation specifiers for std::format	Belfast
P1902	LWG	Missing feature-test macros 2018-2019	Belfast
P1959	LWG	Remove std::weak_equality and std::strong_equality	Belfast
P1960	LWG	NB Comment Changes Reviewed by SG1	Belfast
P1961	LWG	Harmonizing the definitions of total order for pointers	Belfast
P1965	LWG	Blanket Wording for Specifying “Hidden Friends”	Belfast
P0586	LWG	Safe integral comparisons	Prague
P0593	CWG	Implicit creation of objects for low-level object manipulation	Prague
P1115	LWG	Improving the Return Value of Erase-Like Algorithms II: Free erase/erase if	Prague	Complete	11.0
P1243	LWG	Rangify New Algorithms	Prague
P1460	LWG	Mandating the Standard Library: Clause 20 - Utilities library	Prague
P1739	LWG	Avoid template bloat for safe_ranges in combination with “subrange-y” view adaptors	Prague
P1831	LWG	Deprecating volatile: library	Prague
P1868	LWG	width: clarifying units of width and precision in std::format	Prague
P1908	CWG	Reserving Attribute Namespaces for Future Use	Prague
P1937	CWG	Fixing inconsistencies between constexpr and consteval functions	Prague
P1956	LWG	On the names of low-level bit manipulation functions	Prague	Complete	12.0
P1957	CWG	Converting from T* to bool should be considered narrowing (re: US 212)	Prague
P1963	LWG	Fixing US 313	Prague
P1964	LWG	Wording for boolean-testable	Prague
P1970	LWG	Consistency for size() functions: Add ranges::ssize	Prague
P1973	LWG	Rename “_default_init” Functions, Rev1	Prague
P1976	LWG	Fixed-size span construction from dynamic range	Prague	Complete	11.0
P1981	LWG	Rename leap to leap_second	Prague
P1982	LWG	Rename link to time_zone_link	Prague
P1983	LWG	Wording for GB301, US296, US292, US291, and US283	Prague
P1994	LWG	elements_view needs its own sentinel	Prague
P2002	CWG	Defaulted comparison specification cleanups	Prague
P2045	LWG	Missing Mandates for the standard library	Prague
P2085	CWG	Consistent defaulted comparisons	Prague
P2091	LWG	Issues with range access CPOs	Prague
P2101	LWG	‘Models’ subsumes ‘satisfies’ (Wording for US298 and US300)	Prague
P2102	LWG	Make ‘implicit expression variations’ more explicit (Wording for US185)	Prague
P2106	LWG	Alternative wording for GB315 and GB316	Prague
P2116	LWG	Remove tuple-like protocol support from fixed-extent span	Prague	Complete	11.0

Note

1

P0600: The missing bits in P0600 are in §[mem.res.class], §[mem.poly.allocator.class], and §[container.node.overview].

2

P0966: It was previously erroneously marked as complete in version 8.0. See bug 45368.

3

P0619: Only std::allocator part is implemented.

Library Working Group Issues Status

Issue #	Issue Name	Meeting	Status	First released version
2070	allocate_shared should use allocator_traits<A>::construct	Toronto	Resolved by P0674R1
2444	Inconsistent complexity for std::sort_heap	Toronto
2593	Moved-from state of Allocators	Toronto
2597	std::log misspecified for complex numbers	Toronto
2783	stack::emplace() and queue::emplace() should return decltype(auto)	Toronto	Complete
2932	Constraints on parallel algorithm implementations are underspecified	Toronto
2937	Is equivalent("existing_thing", "not_existing_thing") an error	Toronto	Complete
2940	result_of specification also needs a little cleanup	Toronto
2942	LWG 2873’s resolution missed weak_ptr::owner_before	Toronto	Complete
2954	Specialization of the convenience variable templates should be prohibited	Toronto	Complete
2961	Bad postcondition for set_default_resource	Toronto
2966	Incomplete resolution of US 74	Toronto	Nothing To Do
2974	Diagnose out of bounds tuple_element/variant_alternative	Toronto	Complete
2779	[networking.ts] Relax requirements on buffer sequence iterators	Albuquerque
2870	Default value of parameter theta of polar should be dependent	Albuquerque	Complete
2935	What should create_directories do when p already exists but is not a directory?	Albuquerque	Nothing To Do
2941	[thread.req.timing] wording should apply to both member and namespace-level functions	Albuquerque	Nothing To Do
2944	LWG 2905 accidentally removed requirement that construction of the deleter doesn’t throw an exception	Albuquerque	Nothing To Do
2945	Order of template parameters in optional comparisons	Albuquerque	Complete
2948	unique_ptr does not define operator<< for stream output	Albuquerque	Complete
2950	std::byte operations are misspecified	Albuquerque	Complete
2952	iterator_traits should work for pointers to cv T	Albuquerque	Complete
2953	LWG 2853 should apply to deque::erase too	Albuquerque	Complete
2958	Moves improperly defined as deleted	Albuquerque	We already do this
2964	Apparently redundant requirement for dynamic_pointer_cast	Albuquerque
2965	Non-existing path::native_string() in filesystem_error::what() specification	Albuquerque	Nothing To Do
2972	What is is_trivially_destructible_v<int>?	Albuquerque	Complete
2976	Dangling uses_allocator specialization for packaged_task	Albuquerque	Complete
2977	unordered_meow::merge() has incorrect Throws: clause	Albuquerque	Nothing To Do
2978	Hash support for pmr::string and friends	Albuquerque
2979	aligned_union should require complete object types	Albuquerque	Complete
2980	Cannot compare_exchange empty pointers	Albuquerque
2981	Remove redundant deduction guides from standard library	Albuquerque
2982	Making size_type consistent in associative container deduction guides	Albuquerque
2988	Clause 32 cleanup missed one typename	Albuquerque
2993	reference_wrapper<T> conversion from T&&	Albuquerque
2998	Requirements on function objects passed to {forward_,}list-specific algorithms	Albuquerque	Nothing To Do
3001	weak_ptr::element_type needs remove_extent_t	Albuquerque
3024	variant’s copies must be deleted instead of disabled via SFINAE	Albuquerque	Complete
2164	What are the semantics of vector.emplace(vector.begin(), vector.back())?	Jacksonville	Complete
2243	istream::putback problem	Jacksonville	Complete
2816	resize_file has impossible postcondition	Jacksonville	Nothing To Do
2843	Unclear behavior of std::pmr::memory_resource::do_allocate()	Jacksonville	Complete
2849	Why does !is_regular_file(from) cause copy_file to report a “file already exists” error?	Jacksonville	Nothing To Do
2851	std::filesystem enum classes are now underspecified	Jacksonville	Nothing To Do
2946	LWG 2758’s resolution missed further corrections	Jacksonville	Complete
2969	polymorphic_allocator::construct() shouldn’t pass resource()	Jacksonville	Complete
2975	Missing case for pair construction in scoped and polymorphic allocators	Jacksonville
2989	path’s stream insertion operator lets you insert everything under the sun	Jacksonville	Complete
3000	monotonic_memory_resource::do_is_equal uses dynamic_cast unnecessarily	Jacksonville
3002	[networking.ts] basic_socket_acceptor::is_open() isn’t noexcept	Jacksonville
3004	§[string.capacity] and §[vector.capacity] should specify time complexity for capacity()	Jacksonville	Nothing To Do
3005	Destruction order of arrays by make_shared/allocate_shared only recommended?	Jacksonville
3007	allocate_shared should rebind allocator to cv-unqualified value_type for construction	Jacksonville
3009	Including <string_view> doesn’t provide std::size/empty/data	Jacksonville	Complete
3010	[networking.ts] uses_executor says “if a type T::executor_type exists”	Jacksonville
3013	(recursive_)directory_iterator construction and traversal should not be noexcept	Jacksonville	Complete
3014	More noexcept issues with filesystem operations	Jacksonville	Complete
3015	copy_options::*unspecified* underspecified	Jacksonville	Nothing To Do
3017	list splice functions should use addressof	Jacksonville	Complete
3020	[networking.ts] Remove spurious nested value_type buffer sequence requirement	Jacksonville
3026	filesystem::weakly_canonical still defined in terms of canonical(p, base)	Jacksonville	Complete
3030	Who shall meet the requirements of try_lock?	Jacksonville	Nothing To Do
3034	P0767R1 breaks previously-standard-layout types	Jacksonville	Complete
3035	std::allocator’s constructors should be constexpr	Jacksonville	Complete
3039	Unnecessary decay in thread and packaged_task	Jacksonville	Complete
3041	Unnecessary decay in reference_wrapper	Jacksonville	Complete
3042	is_literal_type_v should be inline	Jacksonville	Complete
3043	Bogus postcondition for filesystem_error constructor	Jacksonville	Complete
3045	atomic<*floating-point*> doesn’t have value_type or difference_type	Jacksonville
3048	transform_reduce(exec, first1, last1, first2, init) discards execution policy	Jacksonville
3051	Floating point classifications were inadvertently changed in P0175	Jacksonville	Nothing To Do
3075	basic_string needs deduction guides from basic_string_view	Jacksonville	Complete
2139	What is a user-defined type?	Rapperswil
2970	Return type of std::visit misspecified	Rapperswil
3058	Parallel adjacent_difference shouldn’t require creating temporaries	Rapperswil
3062	Unnecessary decay_t in is_execution_policy_v should be remove_cvref_t	Rapperswil
3067	recursive_directory_iterator::pop must invalidate	Rapperswil	Nothing To Do
3071	[networking.ts] read_until still refers to “input sequence”	Rapperswil	Nothing To Do
3074	Non-member functions for valarray should only deduce from the valarray	Rapperswil
3076	basic_string CTAD ambiguity	Rapperswil	Complete
3079	LWG 2935 forgot to fix the existing_p overloads of create_directory	Rapperswil	Nothing To Do
3080	Floating point from_chars pattern specification breaks round-tripping	Rapperswil
3083	What should ios::iword(-1) do?	Rapperswil	Nothing To Do
3094	[time.duration.io]p4 makes surprising claims about encoding	Rapperswil
3100	Unnecessary and confusing “empty span” wording	Rapperswil	Nothing To Do
3102	Clarify span iterator and const_iterator behavior	Rapperswil	Complete
3104	Fixing duration division	Rapperswil	Complete
2183	Muddled allocator requirements for match_results constructors	San Diego	Complete
2184	Muddled allocator requirements for match_results assignments	San Diego	Complete
2412	promise::set_value() and promise::get_future() should not race	San Diego
2499	operator>>(basic_istream&, CharT*) makes it hard to avoid buffer overflows	San Diego	Resolved by P0487R1
2682	filesystem::copy() won’t create a symlink to a directory	San Diego	Nothing To Do
2697	[concurr.ts] Behavior of future/shared_future unwrapping constructor when given an invalid future	San Diego
2797	Trait precondition violations	San Diego	Resolved by 1285R0
2936	Path comparison is defined in terms of the generic format	San Diego	Complete
2943	Problematic specification of the wide version of basic_filebuf::open	San Diego	Nothing To Do
2960	[fund.ts.v3] nonesuch is insufficiently useless	San Diego	Complete
2995	basic_stringbuf default constructor forbids it from using SSO capacity	San Diego
2996	Missing rvalue overloads for shared_ptr operations	San Diego
3008	make_shared (sub)object destruction semantics are not specified	San Diego
3022	is_convertible<derived*, base*> may lead to ODR	San Diego	Resolved by 1285R0
3025	Map-like container deduction guides should use pair<Key, T>, not pair<const Key, T>	San Diego	Complete
3031	Algorithms and predicates with non-const reference arguments	San Diego
3037	polymorphic_allocator and incomplete types	San Diego
3038	polymorphic_allocator::allocate should not allow integer overflow to create vulnerabilities	San Diego
3054	uninitialized_copy appears to not be able to meet its exception-safety guarantee	San Diego
3065	LWG 2989 missed that all path’s other operators should be hidden friends as well	San Diego	Complete
3096	path::lexically_relative is confused by trailing slashes	San Diego	Complete
3116	*OUTERMOST_ALLOC_TRAITS* needs remove_reference_t	San Diego
3122	__cpp_lib_chrono_udls was accidentally dropped	San Diego	Complete
3127	basic_osyncstream::rdbuf needs a ``const_cast``	San Diego
3128	strstream::rdbuf needs a ``const_cast``	San Diego	Nothing To Do
3129	regex_token_iterator constructor uses wrong pointer arithmetic	San Diego
3130	§[input.output] needs many addressof	San Diego
3131	addressof all the things	San Diego
3132	Library needs to ban macros named expects or ensures	San Diego	Nothing To Do
3134	[fund.ts.v3] LFTSv3 contains extraneous [meta] variable templates that should have been deleted by P09961	San Diego	Resolved by P1210R0
3137	Header for __cpp_lib_to_chars	San Diego	Complete
3145	file_clock breaks ABI for C++17 implementations	San Diego	Complete
3147	Definitions of “likely” and “unlikely” are likely to cause problems	San Diego
3148	<concepts> should be freestanding	San Diego
3153	Common and common_type have too little in common	San Diego
3154	Common and CommonReference have a common defect	San Diego
3012	atomic<T> is unimplementable for non-is_trivially_copy_constructible T	Kona
3040	basic_string_view::starts_with Effects are incorrect	Kona	Complete
3077	(push|emplace)_back should invalidate the end iterator	Kona	Nothing To Do
3087	One final &x in §[list.ops]	Kona	Nothing To Do
3101	span’s Container constructors need another constraint	Kona	Complete
3112	system_error and filesystem_error constructors taking a string may not be able to meet their postconditions	Kona
3119	Program-definedness of closure types	Kona	Nothing To Do
3133	Modernizing numeric type requirements	Kona
3144	span does not have a ``const_pointer`` typedef	Kona	Complete
3173	Enable CTAD for ``ref-view``	Kona
3179	subrange should always model Range	Kona
3180	Inconsistently named return type for ranges::minmax_element	Kona
3182	Specification of Same could be clearer	Kona
2899	is_(nothrow_)move_constructible and tuple, optional and unique_ptr	Cologne
3055	path::operator+=(*single-character*) misspecified	Cologne	Complete	7.0
3158	tuple(allocator_arg_t, const Alloc&) should be conditionally explicit	Cologne
3169	ranges permutation generators discard useful information	Cologne
3183	Normative permission to specialize Ranges variable templates	Cologne
3184	Inconsistencies in bind_front wording	Cologne
3185	Uses-allocator construction functions missing constexpr and noexcept	Cologne
3186	ranges removal, partition, and partial_sort_copy algorithms discard useful information	Cologne
3187	P0591R4 reverted DR 2586 fixes to scoped_allocator_adaptor::construct()	Cologne
3191	std::ranges::shuffle synopsis does not match algorithm definition	Cologne
3196	std::optional<T> is ill-formed is T is an array	Cologne	Complete
3198	Bad constraint on std::span::span()	Cologne	Complete
3199	istream >> bitset<0> fails	Cologne
3202	P0318R1 was supposed to be revised	Cologne	Complete
3206	year_month_day conversion to sys_days uses not-existing member function	Cologne	Complete
3208	Boolean’s expression requirements are ordered inconsistently	Cologne	Nothing To Do
3209	Expression in year::ok() returns clause is ill-formed	Cologne	Complete
3231	year_month_day_last::day specification does not cover !ok() values	Belfast	Nothing To Do
3225	zoned_time converting constructor shall not be noexcept	Belfast
3190	std::allocator::allocate sometimes returns too little storage	Belfast
3218	Modifier for %d parse flag does not match POSIX and format specification	Belfast
3224	zoned_time constructor from TimeZonePtr does not specify initialization of tp_	Belfast
3230	Format specifier %y/%Y is missing locale alternative versions	Belfast
3232	Inconsistency in zoned_time deduction guides	Belfast
3222	P0574R1 introduced preconditions on non-existent parameters	Belfast
3221	Result of year_month arithmetic with months is ambiguous	Belfast	Complete	8.0
3235	parse manipulator without abbreviation is not callable	Belfast
3246	What are the constraints on the template parameter of basic_format_arg?	Belfast
3253	basic_syncbuf::basic_syncbuf() should not be explicit	Belfast
3245	Unnecessary restriction on '%p' parse specifier	Belfast
3244	Constraints for Source in §[fs.path.req] insufficiently constrainty	Belfast
3241	chrono-spec grammar ambiguity in §[time.format]	Belfast
3257	Missing feature testing macro update from P0858	Belfast
3256	Feature testing macro for constexpr algorithms	Belfast
3273	Specify weekday_indexed to range of [0, 7]	Belfast
3070	path::lexically_relative causes surprising results if a filename can also be a root-name	Belfast
3266	to_chars(bool) should be deleted	Belfast
3272	%I%p should parse/format duration since midnight	Belfast
3259	The definition of constexpr iterators should be adjusted	Belfast
3103	Errors in taking subview of span should be ill-formed where possible	Belfast
3274	Missing feature test macro for <span>	Belfast
3276	Class split_view::outer_iterator::value_type should inherit from view_interface	Belfast
3277	Pre-increment on prvalues is not a requirement of weakly_incrementable	Belfast
3149	DefaultConstructible should require default initialization	Belfast
1203	More useful rvalue stream insertion	Prague	Complete	12.0
2859	Definition of reachable in [ptr.launder] misses pointer arithmetic from pointer-interconvertible object	Prague
3018	shared_ptr of function type	Prague
3050	Conversion specification problem in chrono::duration constructor	Prague
3141	CopyConstructible doesn’t preserve source values	Prague
3150	UniformRandomBitGenerator should validate min and max	Prague
3175	The CommonReference requirement of concept SwappableWith is not satisfied in the example	Prague
3194	ConvertibleTo prose does not match code	Prague
3200	midpoint should not constrain T is complete	Prague	Nothing To Do
3201	lerp should be marked as noexcept	Prague	Complete
3226	zoned_time constructor from string_view should accept zoned_time<Duration2, TimeZonePtr2>	Prague
3233	Broken requirements for shared_ptr converting constructors	Prague
3237	LWG 3038 and 3190 have inconsistent PRs	Prague
3238	Insufficiently-defined behavior of std::function deduction guides	Prague
3242	std::format: missing rules for arg-id in width and precision	Prague
3243	std::format and negative zeroes	Prague
3247	ranges::iter_move should perform ADL-only lookup of iter_move	Prague
3248	std::format #b, #B, #o, #x, and #X presentation types misformat negative numbers	Prague
3250	std::format: # (alternate form) for NaN and inf	Prague
3251	Are std::format alignment specifiers applied to string arguments?	Prague
3252	Parse locale’s aware modifiers for commands are not consistent with POSIX spec	Prague
3254	Strike stop_token’s operator!=	Prague
3255	span’s array constructor is too strict	Prague	Complete
3260	year_month* arithmetic rejects durations convertible to years	Prague
3262	Formatting of negative durations is not specified	Prague
3264	sized_range and ranges::size redundantly use disable_sized_range	Prague
3269	Parse manipulators do not specify the result of the extraction from stream	Prague
3270	Parsing and formatting %j with durations	Prague
3280	View converting constructors can cause constraint recursion and are unneeded	Prague
3281	Conversion from *pair-like* types to subrange is a silent semantic promotion	Prague
3282	subrange converting constructor should disallow derived to base conversions	Prague
3284	random_access_iterator semantic constraints accidentally promote difference type using unary negate	Prague
3285	The type of a customization point object shall satisfy semiregular	Prague
3286	ranges::size is not required to be valid after a call to ranges::begin on an input range	Prague
3291	iota_view::iterator has the wrong iterator_category	Prague
3292	iota_view is under-constrained	Prague
3294	zoned_time deduction guides misinterprets string/char*	Prague
3296	Inconsistent default argument for basic_regex<>::assign	Prague	Complete
3299	Pointers don’t need customized iterator behavior	Prague
3300	Non-array ssize overload is underconstrained	Prague
3301	transform_view::iterator has incorrect iterator_category	Prague
3302	Range adaptor objects keys and values are unspecified	Prague
3303	Bad “constexpr” marker for destroy/destroy_n	Prague
3304	Allocate functions of std::polymorphic_allocator should require [[nodiscard]]	Prague
3307	std::allocator<void>().allocate(n)	Prague
3310	Replace SIZE_MAX with numeric_limits<size_t>::max()	Prague
3313	join_view::iterator::operator-- is incorrectly constrained	Prague
3314	Is stream insertion behavior locale dependent when Period::type is micro?	Prague
3315	Correct Allocator Default Behavior	Prague
3316	Correctly define epoch for utc_clock / utc_timepoint	Prague
3317	Incorrect operator<< for floating-point durations	Prague
3318	Clarify whether clocks can represent time before their epoch	Prague
3319	Properly reference specification of IANA time zone database	Prague
3320	span::cbegin/cend methods produce different results than std::[ranges::]cbegin/cend	Prague	Complete
3321	uninitialized_construct_using_allocator should use construct_at	Prague
3323	*has-tuple-element* helper concept needs convertible_to	Prague
3324	Special-case std::strong/weak/partial_order for pointers	Prague
3325	Constrain return type of transformation function for transform_view	Prague
3326	enable_view has false positives	Prague
3327	Format alignment specifiers vs. text direction	Prague
3328	Clarify that std::string is not good for UTF-8	Prague
3329	totally_ordered_with both directly and indirectly requires common_reference_with	Prague
3330	Include <compare> from most library headers	Prague
3331	Define totally_ordered/_with in terms of *partially-ordered-with*	Prague
3332	Issue in §[time.format]	Prague
3334	basic_osyncstream move assignment and destruction calls basic_syncbuf::emit() twice	Prague
3335	Resolve C++20 NB comments US 273 and GB 274	Prague
3338	Rename default_constructible to default_initializable	Prague
3340	Formatting functions should throw on argument/format string mismatch in §[format.functions]	Prague
3346	pair and tuple copy and move constructor have backwards specification	Prague
3347	std::pair<T, U> now requires T and U to be less-than-comparable	Prague
3348	__cpp_lib_unwrap_ref in wrong header	Prague
3349	Missing __cpp_lib_constexpr_complex for P0415R1	Prague
3350	Simplify return type of lexicographical_compare_three_way	Prague
3351	ranges::enable_safe_range should not be constrained	Prague
3352	strong_equality isn’t a thing	Prague
3354	has_strong_structural_equality has a meaningless definition	Prague
3355	The memory algorithms should support move-only input iterators introduced by P1207	Prague
3356	__cpp_lib_nothrow_convertible should be __cpp_lib_is_nothrow_convertible	Prague
3358	§[span.cons] is mistaken that to_address can throw	Prague
3359	<chrono> leap second support should allow for negative leap seconds	Prague
3360	three_way_comparable_with is inconsistent with similar concepts	Prague
3362	Strike stop_source’s operator!=	Prague
3363	drop_while_view should opt-out of sized_range	Prague
3364	Initialize data members of ranges and their iterators	Prague
3367	Integer-class conversions should not throw	Prague
3369	span’s deduction-guide for built-in arrays doesn’t work	Prague
3371	visit_format_arg and make_format_args are not hidden friends	Prague
3372	vformat_to should not try to deduce Out twice	Prague
3373	{to,from}_chars_result and format_to_n_result need the “we really mean what we say” wording	Prague
3374	P0653 + P1006 should have made the other std::to_address overload constexpr	Prague	Complete	12.0
3375	decay in viewable_range should be remove_cvref	Prague
3377	elements_view::iterator befriends a specialization of itself	Prague
3379	“safe” in several library names is misleading	Prague
3380	common_type and comparison categories	Prague
3381	begin and data must agree for contiguous_range	Prague
3382	NTTP for pair and array	Prague
3383	§[time.zone.leap.nonmembers] sys_seconds should be replaced with seconds	Prague
3384	transform_view::*sentinel* has an incorrect operator-	Prague
3385	common_iterator is not sufficiently constrained for non-copyable iterators	Prague
3387	§[range.reverse.view] reverse_view<V> unintentionally requires range<const V>	Prague
3388	view iterator types have ill-formed <=> operators	Prague
3389	A move-only iterator still does not have a counted_iterator	Prague
3390	make_move_iterator() cannot be used to construct a move_iterator for a move-only iterator	Prague
3393	Missing/incorrect feature test macro for coroutines	Prague
3395	Definition for three-way comparison needs to be updated (US 152)	Prague
3396	Clarify point of reference for source_location::current() (DE 169)	Prague
3397	ranges::basic_istream_view::iterator should not provide iterator_category	Prague
3398	tuple_element_t is also wrong for const subrange	Prague

Last Updated: 24-Nov-2020