libc++ C++2c Status

Overview

In June 2023, the C++ standard committee adopted the first changes to the next version of the C++ standard, known here as “C++2c” (probably to be C++26).

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	Labels
P2497R0	LWG	Testing for success or failure of <charconv> functions	Varna June 2023	Complete	18.0
P2592R3	LWG	Hashing support for std::chrono value classes	Varna June 2023
P2587R3	LWG	to_string or not to_string	Varna June 2023			format
P2562R1	LWG	constexpr Stable Sorting	Varna June 2023
P2545R4	LWG	Read-Copy Update (RCU)	Varna June 2023
P2530R3	LWG	Hazard Pointers for C++26	Varna June 2023
P2538R1	LWG	ADL-proof std::projected	Varna June 2023	Complete	18.0	ranges
P2495R3	LWG	Interfacing stringstreams with string_view	Varna June 2023	Complete	19.0
P2510R3	LWG	Formatting pointers	Varna June 2023	Complete [1]	17.0	format
P2198R7	LWG	Freestanding Feature-Test Macros and Implementation-Defined Extensions	Varna June 2023
P2338R4	LWG	Freestanding Library: Character primitives and the C library	Varna June 2023
P2013R5	LWG	Freestanding Language: Optional ::operator new	Varna June 2023
P2363R5	LWG	Extending associative containers with the remaining heterogeneous overloads	Varna June 2023
P1901R2	LWG	Enabling the Use of weak_ptr as Keys in Unordered Associative Containers	Varna June 2023
P1885R12	LWG	Naming Text Encodings to Demystify Them	Varna June 2023
P0792R14	LWG	function_ref: a type-erased callable reference	Varna June 2023
P2874R2	LWG	Mandating Annex D Require No More	Varna June 2023
P2757R3	LWG	Type-checking format args	Varna June 2023			format
P2637R3	LWG	Member visit	Varna June 2023	Complete	19.0
P2641R4	CWG, LWG	Checking if a union alternative is active	Varna June 2023
P1759R6	LWG	Native handles and file streams	Varna June 2023	Complete	18.0
P2697R1	LWG	Interfacing bitset with string_view	Varna June 2023	Complete	18.0
P1383R2	LWG	More constexpr for <cmath> and <complex>	Varna June 2023
P2734R0	LWG	Adding the new SI prefixes	Varna June 2023	Complete	17.0
P2548R6	LWG	copyable_function	Varna June 2023
P2714R1	LWG	Bind front and back to NTTP callables	Varna June 2023
P2630R4	LWG	submdspan	Varna June 2023
P0543R3	LWG	Saturation arithmetic	Kona November 2023	Complete	18.0
P2407R5	LWG	Freestanding Library: Partial Classes	Kona November 2023
P2546R5	LWG	Debugging Support	Kona November 2023
P2905R2	LWG	Runtime format strings	Kona November 2023	Complete	18.0	format Defect Report
P2918R2	LWG	Runtime format strings II	Kona November 2023	Complete	18.0	format
P2909R4	LWG	Fix formatting of code units as integers (Dude, where’s my char?)	Kona November 2023	Complete	18.0	format Defect Report
P0952R2	LWG	A new specification for std::generate_canonical	Kona November 2023
P2447R6	LWG	std::span over an initializer list	Kona November 2023	Complete	18.0
P2821R5	LWG	span.at()	Kona November 2023	Complete	18.0
P2868R3	LWG	Remove Deprecated std::allocator Typedef From C++26	Kona November 2023	Complete	18.0
P2870R3	LWG	Remove basic_string::reserve() From C++26	Kona November 2023	Complete	18.0
P2871R3	LWG	Remove Deprecated Unicode Conversion Facets from C++26	Kona November 2023	Complete	18.0
P2819R2	LWG	Add tuple protocol to complex	Kona November 2023	Complete	19.0
P2937R0	LWG	Freestanding: Remove strtok	Kona November 2023
P2833R2	LWG	Freestanding Library: inout expected span	Kona November 2023
P2836R1	LWG	std::basic_const_iterator should follow its underlying type’s convertibility	Kona November 2023			Defect Report
P2264R7	LWG	Make assert() macro user friendly for C and C++	Kona November 2023
P1673R13	LWG	A free function linear algebra interface based on the BLAS	Kona November 2023
P2875R4	LWG	Undeprecate polymorphic_allocator::destroy for C++26	Tokyo March 2024	Complete	15.0
P2867R2	LWG	Remove Deprecated strstreams From C++26	Tokyo March 2024	Complete	19.0
P2869R4	LWG	Remove Deprecated shared_ptr Atomic Access APIs from C++26	Tokyo March 2024
P2872R3	LWG	Remove wstring_convert From C++26	Tokyo March 2024	Complete	19.0
P3107R5	LWG	Permit an efficient implementation of std::print	Tokyo March 2024			format Defect Report
P3142R0	LWG	Printing Blank Lines with println	Tokyo March 2024	Complete [2]	19.0	format
P2845R8	LWG	Formatting of std::filesystem::path	Tokyo March 2024			format
P0493R5	LWG	Atomic minimum/maximum	Tokyo March 2024
P2542R8	LWG	views::concat	Tokyo March 2024			ranges
P2591R5	LWG	Concatenation of strings and string views	Tokyo March 2024	Complete	19.0
P2248R8	LWG	Enabling list-initialization for algorithms	Tokyo March 2024
P2810R4	LWG	is_debugger_present is_replaceable	Tokyo March 2024
P1068R11	LWG	Vector API for random number generation	Tokyo March 2024
P2944R3	LWG	Comparisons for reference_wrapper	Tokyo March 2024	Partial [3]	19.0
P2642R6	LWG	Padded mdspan layouts	Tokyo March 2024
P3029R1	LWG	Better mdspan’s CTAD	Tokyo March 2024	Complete	19.0
P2747R2	CWG	constexpr placement new	St. Louis June 2024
P2997R1	LWG	Removing the common reference requirement from the indirectly invocable concepts	St. Louis June 2024	Complete [5]	19.0
P2389R2	LWG	dextents Index Type Parameter	St. Louis June 2024	Complete	19.0
P3168R2	LWG	Give std::optional Range Support	St. Louis June 2024			ranges
P3217R0	LWG	Adjoints to ‘Enabling list-initialization for algorithms’: find_last	St. Louis June 2024
P2985R0	LWG	A type trait for detecting virtual base classes	St. Louis June 2024
P0843R14	LWG	inplace_vector	St. Louis June 2024
P3235R3	LWG	std::print more types faster with less memory	St. Louis June 2024			format Defect Report
P2968R2	LWG	Make std::ignore a first-class object	St. Louis June 2024	Complete	19.0
P2075R6	LWG	Philox as an extension of the C++ RNG engines	St. Louis June 2024
P2422R1	LWG	Remove nodiscard annotations from the standard library specification	St. Louis June 2024	Complete [4]	19.0
P2300R10	LWG	std::execution	St. Louis June 2024

Note

[1]

This paper is applied as DR against C++20. (MSVC STL and libstdc++ will do the same.)

[2]

This paper is applied as DR against C++23. (MSVC STL and libstdc++ will do the same.)

[3]

Implemented comparisons for reference_wrapper only.

[4]

Libc++ keeps the nodiscard attributes as a conforming extension.

[5]

This paper is applied as DR against C++20. (MSVC STL and libstdc++ will do the same.)

Library Working Group Issues Status

Issue #	Issue Name	Meeting	Status	First released version	Labels
2994	Needless UB for basic_string and basic_string_view	Varna June 2023	Complete	5.0
3884	flat_foo is missing allocator-extended copy/move constructors	Varna June 2023			flat containers
3885	op should be in [zombie.names]	Varna June 2023	Nothing To Do
3887	Version macro for allocate_at_least	Varna June 2023	Complete	19.0
3893	LWG 3661 broke atomic<shared_ptr<T>> a; a = nullptr;	Varna June 2023
3894	generator::promise_type::yield_value(ranges::elements_of<Rng, Alloc>) should not be noexcept	Varna June 2023
3903	span destructor is redundantly noexcept	Varna June 2023	Complete	7.0
3904	lazy_split_view::outer-iterator’s const-converting constructor isn’t setting trailing_empty_	Varna June 2023			ranges
3905	Type of std::fexcept_t	Varna June 2023	Complete	3.4
3912	enumerate_view::iterator::operator- should be noexcept	Varna June 2023			ranges
3914	Inconsistent template-head of ranges::enumerate_view	Varna June 2023			ranges
3915	Redundant paragraph about expression variations	Varna June 2023			ranges
3925	Concept formattable’s definition is incorrect	Varna June 2023	Complete	17.0	format
3927	Unclear preconditions for operator[] for sequence containers	Varna June 2023	Nothing To Do
3935	template<class X> constexpr complex& operator=(const complex<X>&) has no specification	Varna June 2023	Complete	3.4
3938	Cannot use std::expected monadic ops with move-only error_type	Varna June 2023	Complete	18.0
3940	std::expected<void, E>::value() also needs E to be copy constructible	Varna June 2023	Complete	18.0
2392	“character type” is used but not defined	Kona November 2023
3203	span element access invalidation	Kona November 2023
3305	any_cast<void>	Kona November 2023	Complete	18.0
3431	<=> for containers should require three_way_comparable<T> instead of <=>	Kona November 2023
3749	common_iterator should handle integer-class difference types	Kona November 2023
3809	Is std::subtract_with_carry_engine<uint16_t> supposed to work	Kona November 2023
3892	Incorrect formatting of nested ranges and tuples	Kona November 2023	Complete	17.0	format
3897	inout_ptr will not update raw pointer to 0	Kona November 2023	Complete	19.0
3946	The definition of const_iterator_t should be reworked	Kona November 2023
3947	Unexpected constraints on adjacent_transform_view::base()	Kona November 2023			ranges
3948	possibly-const-range and as-const-pointer should be noexcept	Kona November 2023			ranges
3949	std::atomic<bool>’s trivial destructor dropped in C++17 spec wording	Kona November 2023
3951	[expected.object.swap]: Using value() instead of has_value()	Kona November 2023	Complete	16.0
3953	iter_move for common_iterator and counted_iterator should return decltype(auto)	Kona November 2023			ranges
3957	[container.alloc.reqmts] The value category of v should be claimed	Kona November 2023
3965	Incorrect example in [format.string.escaped] p3 for formatting of combining characters	Kona November 2023	Complete	19.0	format
3970	[mdspan.syn] Missing definition of full_extent_t and full_extent	Kona November 2023
3973	Monadic operations should be ADL-proof	Kona November 2023
3974	mdspan::operator[] should not copy OtherIndexTypes	Kona November 2023
3987	Including <flat_foo> doesn’t provide std::begin/end	Kona November 2023			flat containers
3990	Program-defined specializations of std::tuple and std::variant can’t be properly supported	Kona November 2023
4001	iota_view should provide empty	Kona November 2023	Complete	19.0	ranges
3767	codecvt<charN_t, char8_t, mbstate_t> incorrectly added to locale	Tokyo March 2024
3919	enumerate_view may invoke UB for sized common non-forward underlying ranges	Tokyo March 2024			ranges
3950	std::basic_string_view comparison operators are overspecified	Tokyo March 2024	Complete	18.0
3975	Specializations of basic_format_context should not be permitted	Tokyo March 2024	Nothing To Do		format
3984	ranges::to’s recursion branch may be ill-formed	Tokyo March 2024	Complete	19.0	ranges
4011	"Effects: Equivalent to return" in [span.elem]	Tokyo March 2024	Nothing To Do
4012	common_view::begin/end are missing the simple-view check	Tokyo March 2024			ranges
4013	lazy_split_view::outer-iterator::value_type should not provide default constructor	Tokyo March 2024			ranges
4016	container-insertable checks do not match what container-inserter does	Tokyo March 2024
4023	Preconditions of std::basic_streambuf::setg/setp	Tokyo March 2024	Complete	19.0
4025	Move assignment operator of std::expected<cv void, E> should not be conditionally deleted	Tokyo March 2024
4030	Clarify whether arithmetic expressions in [numeric.sat.func] are mathematical or C++	Tokyo March 2024	Nothing To Do
4031	bad_expected_access<void> member functions should be noexcept	Tokyo March 2024	Complete	16.0
4035	single_view should provide empty	Tokyo March 2024	Complete	19.0	ranges
4036	__alignof_is_defined is only implicitly specified in C++ and not yet deprecated	Tokyo March 2024
4037	Static data members of ctype_base are not yet required to be usable in constant expressions	Tokyo March 2024
4038	std::text_encoding::aliases_view should have constexpr iterators	Tokyo March 2024
4043	“ASCII” is not a registered character encoding	Tokyo March 2024	Nothing To Do
4045	tuple can create dangling references from tuple-like	Tokyo March 2024
4053	Unary call to std::views::repeat does not decay the argument	Tokyo March 2024	Complete	19.0	ranges
4054	Repeating a repeat_view should repeat the view	Tokyo March 2024	Complete	19.0	ranges
3944	Formatters converting sequences of char to sequences of wchar_t	St. Louis June 2024			format
4060	submdspan preconditions do not forbid creating invalid pointer	St. Louis June 2024
4061	Should std::basic_format_context be default-constructible/copyable/movable?	St. Louis June 2024	Complete	19.0	format
4071	reference_wrapper comparisons are not SFINAE-friendly	St. Louis June 2024	Complete	19.0
4074	compatible-joinable-ranges is underconstrained	St. Louis June 2024			ranges
4076	concat_view should be freestanding	St. Louis June 2024
4079	Missing Preconditions in concat_view::iterator`s conversion constructor	St. Louis June 2024			ranges
4082	views::concat(r) is well-formed when r is an output_range	St. Louis June 2024			ranges
4083	views::as_rvalue should reject non-input ranges	St. Louis June 2024			ranges
4096	views::iota(views::iota(0)) should be rejected	St. Louis June 2024			ranges
4098	views::adjacent<0> should reject non-forward ranges	St. Louis June 2024			ranges
4105	ranges::ends_with`s Returns misses difference casting	St. Louis June 2024			ranges
4106	basic_format_args should not be default-constructible	St. Louis June 2024	Complete	19.0	format
3343	Ordering of calls to unlock() and notify_all() in Effects element of notify_all_at_thread_exit() should be reversed	Not Yet Adopted	Complete	16.0
XXXX	The sys_info range should be affected by save	Not Yet Adopted	Complete	19.0