libc++ C++2b Status

Overview

In November 2020, the C++ standard committee adopted the first changes to the next version of the C++ standard, known here as “C++2b” (probably to be C++23).

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
P0881R7	LWG	A Proposal to add stacktrace library	Autumn 2020
P0943R6	LWG	Support C atomics in C++	Autumn 2020
P1048R1	LWG	A proposal for a type trait to detect scoped enumerations	Autumn 2020	Complete	12.0
P1679R3	LWG	string contains function	Autumn 2020	Complete	12.0
P1682R3	LWG	std::to_underlying for enumerations	February 2021	Complete	13.0
P2017R1	LWG	Conditionally borrowed ranges	February 2021
P2160R1	LWG	Locks lock lockables	February 2021
P2162R2	LWG	Inheriting from std::variant	February 2021	Complete	13.0
P2212R2	LWG	Relax Requirements for time_point::clock	February 2021
P2259R1	LWG	Repairing input range adaptors and counted_iterator	February 2021
P0401R6	LWG	Providing size feedback in the Allocator interface	June 2021
P0448R4	LWG	A strstream replacement using span<charT> as buffer	June 2021
P1132R8	LWG	out_ptr - a scalable output pointer abstraction	June 2021
P1328R1	LWG	Making std::type_info::operator== constexpr	June 2021
P1425R4	LWG	Iterators pair constructors for stack and queue	June 2021
P1518R2	LWG	Stop overconstraining allocators in container deduction guides	June 2021	Complete	13.0
P1659R3	LWG	starts_with and ends_with	June 2021
P1951R1	LWG	Default Arguments for pair Forwarding Constructor	June 2021
P1989R2	LWG	Range constructor for std::string_view	June 2021
P2136R3	LWG	invoke_r	June 2021
P2166R1	LWG	A Proposal to Prohibit std::basic_string and std::basic_string_view construction from nullptr	June 2021	Complete	13.0

Library Working Group Issues Status

Issue #	Issue Name	Meeting	Status	First released version
2839	Self-move-assignment of library types, again	November 2020
3117	Missing packaged_task deduction guides	November 2020
3143	monotonic_buffer_resource growth policy is unclear	November 2020
3195	What is the stored pointer value of an empty weak_ptr?	November 2020
3211	std::tuple<> should be trivially constructible	November 2020
3236	Random access iterator requirements lack limiting relational operators domain to comparing those from the same range	November 2020
3265	move_iterator’s conversions are more broken after P1207	November 2020	Fixed by LWG3435
3435	three_way_comparable_with<reverse_iterator<int*>, reverse_iterator<const int*>>	November 2020	Complete	13.0
3432	Missing requirement for comparison_category	November 2020
3447	Deduction guides for take_view and drop_view have different constraints	November 2020
3450	The const overloads of take_while_view::begin/end are underconstrained	November 2020
3464	istream::gcount() can overflow	November 2020
2731	Existence of lock_guard<MutexTypes...>::mutex_type typedef unclear	November 2020
2743	P0083R3 node_handle private members missing “exposition only” comment	November 2020
2820	Clarify <cstdint> macros	November 2020
3120	Unclear behavior of monotonic_buffer_resource::release()	November 2020
3170	is_always_equal added to std::allocator makes the standard library treat derived types as always equal	November 2020
3036	polymorphic_allocator::destroy is extraneous	November 2020
3171	LWG2989 breaks directory_entry stream insertion	November 2020
3306	ranges::advance violates its preconditions	November 2020
3403	Domain of ranges::ssize(E) doesn’t match ranges::size(E)	November 2020
3404	Finish removing subrange’s conversions from pair-like	November 2020
3405	common_view’s converting constructor is bad, too	November 2020
3406	elements_view::begin() and elements_view::end() have incompatible constraints	November 2020
3419	[algorithms.requirements]/15 doesn’t reserve as many rights as it intends to	November 2020
3420	cpp17-iterator should check that the type looks like an iterator first	November 2020
3421	Imperfect ADL emulation for boolean-testable	November 2020
3425	condition_variable_any fails to constrain its Lock parameters	November 2020
3426	operator<=>(const unique_ptr<T, D>&, nullptr_t) can’t get no satisfaction	November 2020
3427	operator<=>(const shared_ptr<T>&, nullptr_t) definition ill-formed	November 2020
3428	single_view’s in place constructor should be explicit	November 2020
3434	ios_base never reclaims memory for iarray and parray	November 2020
3437	__cpp_lib_polymorphic_allocator is in the wrong header	November 2020
3446	indirectly_readable_traits ambiguity for types with both value_type and element_type	November 2020
3448	transform_view’s sentinel<false> not comparable with iterator<true>	November 2020
3449	take_view and take_while_view’s sentinel<false> not comparable with their const iterator	November 2020
3453	Generic code cannot call ranges::advance(i, s)	November 2020
3455	Incorrect Postconditions on unique_ptr move assignment	November 2020	Nothing To Do
3460	Unimplementable noop_coroutine_handle guarantees	November 2020
3461	convertible_to’s description mishandles cv-qualified void	November 2020
3465	compare_partial_order_fallback requires F < E	November 2020
3466	Specify the requirements for promise/future/shared_future consistently	November 2020
3467	bool can’t be an integer-like type	November 2020
3472	counted_iterator is missing preconditions	November 2020
3473	Normative encouragement in non-normative note	November 2020
3474	Nesting join_views is broken because of CTAD	November 2020
3476	thread and jthread constructors require that the parameters be move-constructible but never move construct the parameters	November 2020
3477	Simplify constraints for semiregular-box	November 2020
3482	drop_view’s const begin should additionally require sized_range	November 2020
3483	transform_view::iterator’s difference is overconstrained	November 2020
3391	Problems with counted_iterator/move_iterator::base() const &	February 2021
3433	subrange::advance(n) has UB when n < 0	February 2021
3490	ranges::drop_while_view::begin() is missing a precondition	February 2021
3492	Minimal improvements to elements_view::iterator	February 2021
3494	Allow ranges to be conditionally borrowed	February 2021	Superseded by P2017R1
3495	constexpr launder makes pointers to inactive members of unions usable	February 2021
3500	join_view::iterator::operator->() is bogus	February 2021
3502	elements_view should not be allowed to return dangling reference	February 2021
3505	split_view::outer-iterator::operator++ misspecified	February 2021
2774	std::function construction vs assignment	June 2021
2818	::std:: everywhere rule needs tweaking	June 2021
2997	LWG 491 and the specification of {forward_,}list::unique	June 2021
3410	lexicographical_compare_three_way is overspecified	June 2021
3430	std::fstream & co. should be constructible from string_view	June 2021
3462	§[formatter.requirements]: Formatter requirements forbid use of fc.arg()	June 2021
3481	viewable_range mishandles lvalue move-only views	June 2021
3506	Missing allocator-extended constructors for priority_queue	June 2021
3517	join_view::iterator’s iter_swap is underconstrained	June 2021
3518	Exception requirements on char trait operations unclear	June 2021
3519	Incomplete synopses for <random> classes	June 2021
3520	iter_move and iter_swap are inconsistent for transform_view::iterator	June 2021
3521	Overly strict requirements on qsort and bsearch	June 2021
3522	Missing requirement on InputIterator template parameter for priority_queue constructors	June 2021
3523	iota_view::sentinel is not always iota_view’s sentinel	June 2021
3526	Return types of uses_allocator_construction_args unspecified	June 2021
3527	uses_allocator_construction_args handles rvalue pairs of rvalue references incorrectly	June 2021
3528	make_from_tuple can perform (the equivalent of) a C-style cast	June 2021
3529	priority_queue(first, last) should construct c with (first, last)	June 2021
3530	BUILTIN-PTR-MEOW should not opt the type out of syntactic checks	June 2021
3532	split_view<V, P>::inner-iterator<true>::operator++(int) should depend on Base	June 2021
3533	Make base() const & consistent across iterator wrappers that supports input_iterators	June 2021
3536	Should chrono::from_stream() assign zero to duration for failure?	June 2021
3539	format_to must not copy models of output_iterator<const charT&>	June 2021
3540	§[format.arg] There should be no const in basic_format_arg(const T* p)	June 2021
3541	indirectly_readable_traits should be SFINAE-friendly for all types	June 2021
3542	basic_format_arg mishandles basic_string_view with custom traits	June 2021
3543	Definition of when counted_iterators refer to the same sequence isn’t quite right	June 2021
3544	format-arg-store::args is unintentionally not exposition-only	June 2021
3546	common_iterator’s postfix-proxy is not quite right	June 2021
3548	shared_ptr construction from unique_ptr should move (not copy) the deleter	June 2021
3549	view_interface is overspecified to derive from view_base	June 2021
3551	borrowed_{iterator,subrange}_t are overspecified	June 2021
3552	Parallel specialized memory algorithms should require forward iterators	June 2021
3553	Useless constraint in split_view::outer-iterator::value_type::begin()	June 2021
3555	{transform,elements}_view::iterator::iterator_concept should consider const-qualification of the underlying range	June 2021

Last Updated: 22-July-2021