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 #	Paper Name	Meeting	Status	First released version	Notes
P2497R0	Testing for success or failure of <charconv> functions	2023-06 (Varna)	Complete	18
P2592R3	Hashing support for std::chrono value classes	2023-06 (Varna)
P2587R3	to_string or not to_string	2023-06 (Varna)
P2562R1	constexpr Stable Sorting	2023-06 (Varna)	Complete	21
P2545R4	Read-Copy Update (RCU)	2023-06 (Varna)
P2530R3	Hazard Pointers for C++26	2023-06 (Varna)
P2538R1	ADL-proof std::projected	2023-06 (Varna)	Complete	18
P2495R3	Interfacing stringstreams with string_view	2023-06 (Varna)	Complete	19
P2510R3	Formatting pointers	2023-06 (Varna)	Complete	17	Implemented as a DR against C++20. (MSVC STL and libstdc++ will do the same.)
P2198R7	Freestanding Feature-Test Macros and Implementation-Defined Extensions	2023-06 (Varna)
P2338R4	Freestanding Library: Character primitives and the C library	2023-06 (Varna)
P2013R5	Freestanding Language: Optional ::operator new	2023-06 (Varna)
P2363R5	Extending associative containers with the remaining heterogeneous overloads	2023-06 (Varna)
P1901R2	Enabling the Use of weak_ptr as Keys in Unordered Associative Containers	2023-06 (Varna)
P1885R12	Naming Text Encodings to Demystify Them	2023-06 (Varna)
P0792R14	function_ref: a type-erased callable reference	2023-06 (Varna)
P2874R2	P2874R2: Mandating Annex D Require No More	2023-06 (Varna)	Complete	12
P2757R3	Type-checking format args	2023-06 (Varna)
P2637R3	Member visit	2023-06 (Varna)	Complete	19	Change of __cpp_lib_variant is completed in LLVM 20. Change of __cpp_lib_format is blocked by P2419R2.
P2641R4	Checking if a union alternative is active	2023-06 (Varna)
P1759R6	Native handles and file streams	2023-06 (Varna)	Complete	18
P2697R1	Interfacing bitset with string_view	2023-06 (Varna)	Complete	18
P1383R2	More constexpr for <cmath> and <complex>	2023-06 (Varna)
P2734R0	Adding the new SI prefixes	2023-06 (Varna)	Complete	17
P2548R6	copyable_function	2023-06 (Varna)
P2714R1	Bind front and back to NTTP callables	2023-06 (Varna)	Partial	20
P2630R4	submdspan	2023-06 (Varna)
P0543R3	Saturation arithmetic	2023-11 (Kona)	Complete	18
P2407R5	Freestanding Library: Partial Classes	2023-11 (Kona)
P2546R5	Debugging Support	2023-11 (Kona)
P2905R2	Runtime format strings	2023-11 (Kona)	Complete	18
P2918R2	Runtime format strings II	2023-11 (Kona)	Complete	18
P2909R4	Fix formatting of code units as integers (Dude, where’s my char?)	2023-11 (Kona)	Complete	18
P0952R2	A new specification for std::generate_canonical	2023-11 (Kona)
P2447R6	std::span over an initializer list	2023-11 (Kona)	Complete	18
P2821R5	span.at()	2023-11 (Kona)	Complete	18
P2868R3	Remove Deprecated std::allocator Typedef From C++26	2023-11 (Kona)	Complete	18
P2870R3	Remove basic_string::reserve() From C++26	2023-11 (Kona)	Complete	18
P2871R3	Remove Deprecated Unicode Conversion Facets from C++26	2023-11 (Kona)	Complete	18
P2819R2	Add tuple protocol to complex	2023-11 (Kona)	Complete	19
P2937R0	Freestanding: Remove strtok	2023-11 (Kona)
P2833R2	Freestanding Library: inout expected span	2023-11 (Kona)
P2836R1	std::basic_const_iterator should follow its underlying type’s convertibility	2023-11 (Kona)
P2264R7	Make assert() macro user friendly for C and C++	2023-11 (Kona)
P1673R13	A free function linear algebra interface based on the BLAS	2023-11 (Kona)
P2875R4	Undeprecate polymorphic_allocator::destroy for C++26	2024-03 (Tokyo)	Complete	15
P2867R2	Remove Deprecated strstreams From C++26	2024-03 (Tokyo)	Complete	19
P2869R4	Remove Deprecated shared_ptr Atomic Access APIs from C++26	2024-03 (Tokyo)
P2872R3	Remove wstring_convert From C++26	2024-03 (Tokyo)	Complete	19
P3107R5	Permit an efficient implementation of std::print	2024-03 (Tokyo)
P3142R0	Printing Blank Lines with println	2024-03 (Tokyo)	Complete	19	Implemented as a DR against C++23. (MSVC STL and libstdc++ will do the same.)
P2845R8	Formatting of std::filesystem::path	2024-03 (Tokyo)
P0493R5	Atomic minimum/maximum	2024-03 (Tokyo)
P2542R8	views::concat	2024-03 (Tokyo)
P2591R5	Concatenation of strings and string views	2024-03 (Tokyo)	Complete	19
P2248R8	Enabling list-initialization for algorithms	2024-03 (Tokyo)
P2810R4	is_debugger_present is_replaceable	2024-03 (Tokyo)
P1068R11	Vector API for random number generation	2024-03 (Tokyo)
P2944R3	Comparisons for reference_wrapper	2024-03 (Tokyo)	Partial		Implemented changes to reference_wrapper and pair
P2642R6	Padded mdspan layouts	2024-03 (Tokyo)
P3029R1	Better mdspan’s CTAD	2024-03 (Tokyo)	Complete	19
P2747R2	constexpr placement new	2024-06 (St. Louis)	Complete	20
P2997R1	Removing the common reference requirement from the indirectly invocable concepts	2024-06 (St. Louis)	Complete	19	Implemented as a DR against C++20. (MSVC STL and libstdc++ will do the same.)
P2389R2	dextents Index Type Parameter	2024-06 (St. Louis)	Complete	19
P3168R2	Give std::optional Range Support	2024-06 (St. Louis)
P3217R0	Adjoints to ‘Enabling list-initialization for algorithms’: find_last	2024-06 (St. Louis)
P2985R0	A type trait for detecting virtual base classes	2024-06 (St. Louis)	Complete	20
P0843R14	inplace_vector	2024-06 (St. Louis)
P3235R3	std::print more types faster with less memory	2024-06 (St. Louis)
P2968R2	Make std::ignore a first-class object	2024-06 (St. Louis)	Complete	19
P2075R6	Philox as an extension of the C++ RNG engines	2024-06 (St. Louis)
P2422R1	Remove nodiscard annotations from the standard library specification	2024-06 (St. Louis)	Complete	19	nodiscard attributes were kept as a conforming extension
P2300R10	std::execution	2024-06 (St. Louis)
P3136R1	Retiring niebloids	2024-11 (Wrocław)	Complete	14
P3138R5	views::cache_latest	2024-11 (Wrocław)
P3379R0	Constrain std::expected equality operators	2024-11 (Wrocław)	Complete	21
P2862R1	text_encoding::name() should never return null values	2024-11 (Wrocław)
P2897R7	aligned_accessor: An mdspan accessor expressing pointer over-alignment	2024-11 (Wrocław)	Complete	21
P3355R1	Fix submdspan for C++26	2024-11 (Wrocław)
P3222R0	Fix C++26 by adding transposed special cases for P2642 layouts	2024-11 (Wrocław)
P3050R2	Fix C++26 by optimizing linalg::conjugated for noncomplex value types	2024-11 (Wrocław)
P3396R1	std::execution wording fixes	2024-11 (Wrocław)
P2835R7	Expose std::atomic_ref’s object address	2024-11 (Wrocław)
P3323R1	cv-qualified types in atomic and atomic_ref	2024-11 (Wrocław)
P3508R0	Wording for “constexpr for specialized memory algorithms”	2024-11 (Wrocław)
P3369R0	constexpr for uninitialized_default_construct	2024-11 (Wrocław)
P3370R1	Add new library headers from C23	2024-11 (Wrocław)
P3309R3	constexpr atomic and atomic_ref	2024-11 (Wrocław)
P1928R15	std::simd — merge data-parallel types from the Parallelism TS 2	2024-11 (Wrocław)
P3325R5	A Utility for Creating Execution Environments	2024-11 (Wrocław)
P3068R6	Allowing exception throwing in constant-evaluation	2024-11 (Wrocław)
P3247R2	Deprecate the notion of trivial types	2024-11 (Wrocław)	Complete	21
P3074R7	trivial unions (was std::uninitialized)	2025-02 (Hagenberg)
P1494R5	Partial program correctness	2025-02 (Hagenberg)
P2900R14	Contracts for C++	2025-02 (Hagenberg)
P3475R2	Defang and deprecate memory_order::consume	2025-02 (Hagenberg)
P2786R13	Trivial Relocatability For C++26	2025-02 (Hagenberg)
P3137R3	views::to_input	2025-02 (Hagenberg)
P0472R3	Put std::monostate in <utility>	2025-02 (Hagenberg)	Complete	21
P3349R1	Converting contiguous iterators to pointers	2025-02 (Hagenberg)
P3372R3	constexpr containers and adaptors	2025-02 (Hagenberg)
P3378R2	constexpr exception types	2025-02 (Hagenberg)
P3441R2	Rename simd_split to simd_chunk	2025-02 (Hagenberg)
P3287R3	Exploration of namespaces for std::simd	2025-02 (Hagenberg)
P2976R1	Freestanding Library: algorithm, numeric, and random	2025-02 (Hagenberg)
P3430R3	simd issues: explicit, unsequenced, identity-element position, and members of disabled simd	2025-02 (Hagenberg)
P2663R7	Interleaved complex values support in std::simd	2025-02 (Hagenberg)
P2933R4	Extend <bit> header function with overloads for std::simd	2025-02 (Hagenberg)
P2846R6	reserve_hint: Eagerly reserving memory for not-quite-sized lazy ranges	2025-02 (Hagenberg)
P3471R4	Standard Library Hardening	2025-02 (Hagenberg)
P0447R28	Introduction of std::hive to the standard library	2025-02 (Hagenberg)
P3019R14	indirect and polymorphic: Vocabulary Types for Composite Class Design	2025-02 (Hagenberg)

Library Working Group Issues Status

Issue #	Issue Name	Meeting	Status	First released version	Notes
LWG2994	Needless UB for basic_string and basic_string_view	2023-06 (Varna)	Complete	5
LWG3884	flat_foo is missing allocator-extended copy/move constructors	2023-06 (Varna)
LWG3885	op should be in [zombie.names]	2023-06 (Varna)	Nothing To Do
LWG3887	Version macro for allocate_at_least	2023-06 (Varna)	Complete	19
LWG3893	LWG 3661 broke atomic<shared_ptr<T>> a; a = nullptr;	2023-06 (Varna)
LWG3894	generator::promise_type::yield_value(ranges::elements_of<Rng, Alloc>) should not be noexcept	2023-06 (Varna)
LWG3903	span destructor is redundantly noexcept	2023-06 (Varna)	Complete	7
LWG3904	lazy_split_view::outer-iterator’s const-converting constructor isn’t setting trailing_empty_	2023-06 (Varna)
LWG3905	Type of std::fexcept_t	2023-06 (Varna)	Complete	3.4
LWG3912	enumerate_view::iterator::operator- should be noexcept	2023-06 (Varna)
LWG3914	Inconsistent template-head of ranges::enumerate_view	2023-06 (Varna)
LWG3915	Redundant paragraph about expression variations	2023-06 (Varna)
LWG3925	Concept formattable’s definition is incorrect	2023-06 (Varna)	Complete	17
LWG3927	Unclear preconditions for operator[] for sequence containers	2023-06 (Varna)	Nothing To Do
LWG3935	template<class X> constexpr complex& operator=(const complex<X>&) has no specification	2023-06 (Varna)	Complete	3.4
LWG3938	Cannot use std::expected monadic ops with move-only error_type	2023-06 (Varna)	Complete	18
LWG3940	std::expected<void, E>::value() also needs E to be copy constructible	2023-06 (Varna)	Complete	18
LWG2392	“character type” is used but not defined	2023-11 (Kona)
LWG3203	span element access invalidation	2023-11 (Kona)	Nothing To Do
LWG3305	any_cast<void>	2023-11 (Kona)	Complete	18
LWG3431	<=> for containers should require three_way_comparable<T> instead of <=>	2023-11 (Kona)
LWG3749	common_iterator should handle integer-class difference types	2023-11 (Kona)
LWG3809	Is std::subtract_with_carry_engine<uint16_t> supposed to work	2023-11 (Kona)
LWG3892	Incorrect formatting of nested ranges and tuples	2023-11 (Kona)	Complete	17
LWG3897	inout_ptr will not update raw pointer to 0	2023-11 (Kona)	Complete	19
LWG3946	The definition of const_iterator_t should be reworked	2023-11 (Kona)
LWG3947	Unexpected constraints on adjacent_transform_view::base()	2023-11 (Kona)
LWG3948	possibly-const-range and as-const-pointer should be noexcept	2023-11 (Kona)
LWG3949	std::atomic<bool>’s trivial destructor dropped in C++17 spec wording	2023-11 (Kona)
LWG3951	[expected.object.swap]: Using value() instead of has_value()	2023-11 (Kona)	Complete	16
LWG3953	iter_move for common_iterator and counted_iterator should return decltype(auto)	2023-11 (Kona)	Complete	20
LWG3957	[container.alloc.reqmts] The value category of v should be claimed	2023-11 (Kona)
LWG3965	Incorrect example in [format.string.escaped] p3 for formatting of combining characters	2023-11 (Kona)	Complete	19
LWG3970	[mdspan.syn] Missing definition of full_extent_t and full_extent	2023-11 (Kona)
LWG3973	Monadic operations should be ADL-proof	2023-11 (Kona)
LWG3974	mdspan::operator[] should not copy OtherIndexTypes	2023-11 (Kona)
LWG3987	Including <flat_foo> doesn’t provide std::begin/end	2023-11 (Kona)
LWG3990	Program-defined specializations of std::tuple and std::variant can’t be properly supported	2023-11 (Kona)	Complete	21
LWG4001	iota_view should provide empty	2023-11 (Kona)	Complete	19
LWG3767	codecvt<charN_t, char8_t, mbstate_t> incorrectly added to locale	2024-03 (Tokyo)
LWG3919	enumerate_view may invoke UB for sized common non-forward underlying ranges	2024-03 (Tokyo)
LWG3950	std::basic_string_view comparison operators are overspecified	2024-03 (Tokyo)	Complete	18
LWG3975	Specializations of basic_format_context should not be permitted	2024-03 (Tokyo)	Nothing To Do
LWG3984	ranges::to’s recursion branch may be ill-formed	2024-03 (Tokyo)	Complete	19
LWG4011	"Effects: Equivalent to return" in [span.elem]	2024-03 (Tokyo)	Nothing To Do
LWG4012	common_view::begin/end are missing the simple-view check	2024-03 (Tokyo)
LWG4013	lazy_split_view::outer-iterator::value_type should not provide default constructor	2024-03 (Tokyo)
LWG4016	container-insertable checks do not match what container-inserter does	2024-03 (Tokyo)	Complete	20
LWG4023	Preconditions of std::basic_streambuf::setg/setp	2024-03 (Tokyo)	Complete	19
LWG4025	Move assignment operator of std::expected<cv void, E> should not be conditionally deleted	2024-03 (Tokyo)	Complete	20
LWG4030	Clarify whether arithmetic expressions in [numeric.sat.func] are mathematical or C++	2024-03 (Tokyo)	Nothing To Do
LWG4031	bad_expected_access<void> member functions should be noexcept	2024-03 (Tokyo)	Complete	16
LWG4035	single_view should provide empty	2024-03 (Tokyo)	Complete	19
LWG4036	__alignof_is_defined is only implicitly specified in C++ and not yet deprecated	2024-03 (Tokyo)
LWG4037	Static data members of ctype_base are not yet required to be usable in constant expressions	2024-03 (Tokyo)
LWG4038	std::text_encoding::aliases_view should have constexpr iterators	2024-03 (Tokyo)
LWG4043	“ASCII” is not a registered character encoding	2024-03 (Tokyo)	Nothing To Do
LWG4045	tuple can create dangling references from tuple-like	2024-03 (Tokyo)
LWG4053	Unary call to std::views::repeat does not decay the argument	2024-03 (Tokyo)	Complete	19
LWG4054	Repeating a repeat_view should repeat the view	2024-03 (Tokyo)	Complete	19
LWG3944	Formatters converting sequences of char to sequences of wchar_t	2024-06 (St. Louis)	Complete	21
LWG4060	submdspan preconditions do not forbid creating invalid pointer	2024-06 (St. Louis)
LWG4061	Should std::basic_format_context be default-constructible/copyable/movable?	2024-06 (St. Louis)	Complete	19
LWG4071	reference_wrapper comparisons are not SFINAE-friendly	2024-06 (St. Louis)	Complete	19
LWG4074	compatible-joinable-ranges is underconstrained	2024-06 (St. Louis)
LWG4076	concat_view should be freestanding	2024-06 (St. Louis)
LWG4079	Missing Preconditions in concat_view::iterator`s conversion constructor	2024-06 (St. Louis)
LWG4082	views::concat(r) is well-formed when r is an output_range	2024-06 (St. Louis)
LWG4083	views::as_rvalue should reject non-input ranges	2024-06 (St. Louis)
LWG4096	views::iota(views::iota(0)) should be rejected	2024-06 (St. Louis)
LWG4098	views::adjacent<0> should reject non-forward ranges	2024-06 (St. Louis)
LWG4105	ranges::ends_with`s Returns misses difference casting	2024-06 (St. Louis)
LWG4106	basic_format_args should not be default-constructible	2024-06 (St. Louis)	Complete	19
LWG3216	Rebinding the allocator before calling construct/destroy in allocate_shared	2024-11 (Wrocław)
LWG3436	std::construct_at should support arrays	2024-11 (Wrocław)
LWG3886	Monad mo’ problems	2024-11 (Wrocław)
LWG3899	co_yielding elements of an lvalue generator is unnecessarily inefficient	2024-11 (Wrocław)
LWG3900	The allocator_arg_t overloads of generator::promise_type::operator new should not be constrained	2024-11 (Wrocław)
LWG3918	std::uninitialized_move/_n and guaranteed copy elision	2024-11 (Wrocław)
LWG4014	LWG 3809 changes behavior of some existing std::subtract_with_carry_engine code	2024-11 (Wrocław)
LWG4024	Underspecified destruction of objects created in std::make_shared_for_overwrite/std::allocate_shared_for_overwrite	2024-11 (Wrocław)		16
LWG4027	possibly-const-range should prefer returning const R&	2024-11 (Wrocław)
LWG4044	Confusing requirements for std::print on POSIX platforms	2024-11 (Wrocław)
LWG4064	Clarify that std::launder is not needed when using the result of std::memcpy	2024-11 (Wrocław)
LWG4072	std::optional comparisons: constrain harder	2024-11 (Wrocław)
LWG4084	std::fixed ignores std::uppercase	2024-11 (Wrocław)
LWG4085	ranges::generate_random’s helper lambda should specify the return type	2024-11 (Wrocław)
LWG4088	println ignores the locale imbued in std::ostream	2024-11 (Wrocław)	Complete	18
LWG4112	has-arrow should required operator->() to be const-qualified	2024-11 (Wrocław)
LWG4113	Disallow has_unique_object_representations<Incomplete[]>	2024-11 (Wrocław)
LWG4119	generator::promise_type::yield_value(ranges::elements_of<R, Alloc>)’s nested generator may be ill-formed	2024-11 (Wrocław)
LWG4124	Cannot format zoned_time with resolution coarser than seconds	2024-11 (Wrocław)
LWG4126	Some feature-test macros for fully freestanding features are not yet marked freestanding	2024-11 (Wrocław)
LWG4134	Issue with Philox algorithm specification	2024-11 (Wrocław)
LWG4135	The helper lambda of std::erase for list should specify return type as bool	2024-11 (Wrocław)	Complete	21
LWG4140	Useless default constructors for bit reference types	2024-11 (Wrocław)	Nothing To Do
LWG4141	Improve prohibitions on “additional storage”	2024-11 (Wrocław)
LWG4142	format_parse_context::check_dynamic_spec should require at least one type	2024-11 (Wrocław)
LWG4144	Disallow unique_ptr<T&, D>	2024-11 (Wrocław)
LWG4147	Precondition on inplace_vector::emplace	2024-11 (Wrocław)
LWG4148	unique_ptr::operator* should not allow dangling references	2024-11 (Wrocław)
LWG4153	Fix extra “-1” for philox_engine::max()	2024-11 (Wrocław)
LWG4154	The Mandates for std::packaged_task’s constructor from a callable entity should consider decaying	2024-11 (Wrocław)
LWG4157	The resolution of LWG3465 was damaged by P2167R3	2024-11 (Wrocław)		20
LWG4164	Missing guarantees for forward_list modifiers	2024-11 (Wrocław)
LWG4169	std::atomic<T>’s default constructor should be constrained	2024-11 (Wrocław)
LWG4170	contiguous_iterator should require to_address(I{})	2024-11 (Wrocław)
LWG3578	Iterator SCARYness in the context of associative container merging	2025-02 (Hagenberg)
LWG3956	chrono::parse uses from_stream as a customization point	2025-02 (Hagenberg)
LWG4172	unique_lock self-move-assignment is broken	2025-02 (Hagenberg)
LWG4175	get_env() specified in terms of as_const() but this doesn’t work with rvalue senders	2025-02 (Hagenberg)
LWG4179	Wrong range in [alg.search]	2025-02 (Hagenberg)
LWG4186	regex_traits::transform_primary mistakenly detects typeid of a function	2025-02 (Hagenberg)
LWG4189	cache_latest_view should be freestanding	2025-02 (Hagenberg)
LWG4191	P1467 changed the return type of pow(complex<float>, int)	2025-02 (Hagenberg)
LWG4196	Complexity of inplace_merge() is incorrect	2025-02 (Hagenberg)
LWG3343	Ordering of calls to unlock() and notify_all() in Effects element of notify_all_at_thread_exit() should be reversed	Not Adopted Yet	Complete	16
LWG4139	§[time.zone.leap] recursive constraint in <=>	Not Adopted Yet	Complete	20
LWG3456	Pattern used by std::from_chars is underspecified (option B)	Not Adopted Yet	Complete	20