libc++ C++2a Status

In July 2017, the C++ standard committee created a draft for the next version of the C++ standard, known here as "C++2a" (probably to be C++20).

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

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

The groups that have contributed papers:

Paper Status

Paper #GroupPaper NameMeetingStatusFirst released version
P0463R1LWGEndian just EndianTorontoComplete7.0
P0674R1LWGExtending make_shared to Support ArraysToronto
P0020R6LWGFloating Point AtomicAlbuquerque
P0053R7LWGC++ Synchronized Buffered OstreamAlbuquerque
P0202R3LWGAdd constexpr modifiers to functions in <algorithm> and <utility> HeadersAlbuquerqueIn Progress7.0
P0415R1LWGConstexpr for std::complexAlbuquerqueIn Progress7.0
P0439R0LWGMake std::memory_order a scoped enumerationAlbuquerque
P0457R2LWGString Prefix and Suffix CheckingAlbuquerqueComplete6.0
P0550R2LWGTransformation Trait remove_cvrefAlbuquerqueComplete6.0
P0600R1LWGnodiscard in the LibraryAlbuquerqueIn Progress7.0
P0616R0LWGde-pessimize legacy algorithms with std::moveAlbuquerque
P0653R2LWGUtility to convert a pointer to a raw pointerAlbuquerqueComplete6.0
P0718R2LWGAtomic shared_ptrAlbuquerque
P0767R1CWGDeprecate PODAlbuquerqueComplete7.0
P0768R1CWGLibrary Support for the Spaceship (Comparison) OperatorAlbuquerque
P0777R1LWGTreating Unnecessary decayAlbuquerqueComplete7.0
P0122R7LWG<span>JacksonvilleIn Progress
P0355R7LWGExtending chrono to Calendars and Time ZonesJacksonville
P0551R3LWGThou Shalt Not Specialize std Function Templates!Jacksonville
P0753R2LWGManipulators for C++ Synchronized Buffered OstreamJacksonville
P0754R2LWG<version>JacksonvilleComplete7.0
P0809R0LWGComparing Unordered ContainersJacksonville
P0858R0LWGConstexpr iterator requirementsJacksonville
P0905R1CWGSymmetry for spaceshipJacksonville
P0966R1LWGstring::reserve Should Not ShrinkJacksonville

[ Note: "Nothing to do" means that no library changes were needed to implement this change -- end note]

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

The missing bits in P0202 are in copy, copy_backwards, move, and move_backwards (and the ones that call them: copy_n, rotate_copy, merge, set_union, set_difference, and set_symmetric_difference). This is because the first four algorithms have specializations that call memmove which is not constexpr. See Bug 25165

Library Working group Issues Status

Issue #Issue NameMeetingStatus
2070allocate_shared should use allocator_traits<A>::constructTorontoResolved by P0674R1
2444Inconsistent complexity for std::sort_heapToronto
2593Moved-from state of AllocatorsToronto
2597std::log misspecified for complex numbersToronto
2783stack::emplace() and queue::emplace() should return decltype(auto)TorontoComplete
2932Constraints on parallel algorithm implementations are underspecifiedToronto
2937Is equivalent("existing_thing", "not_existing_thing") an errorTorontoComplete
2940result_of specification also needs a little cleanupToronto
2942LWG 2873's resolution missed weak_ptr::owner_beforeTorontoComplete
2954Specialization of the convenience variable templates should be prohibitedTorontoComplete
2961Bad postcondition for set_default_resourceToronto
2966Incomplete resolution of US 74TorontoNothing to do
2974Diagnose out of bounds tuple_element/variant_alternativeTorontoComplete
2779[networking.ts] Relax requirements on buffer sequence iteratorsAlbuquerque
2870Default value of parameter theta of polar should be dependentAlbuquerqueComplete
2935What should create_directories do when p already exists but is not a directory?Albuquerque
2941[thread.req.timing] wording should apply to both member and namespace-level functionsAlbuquerqueNothing to do
2944LWG 2905 accidentally removed requirement that construction of the deleter doesn't throw an exceptionAlbuquerqueNothing to do
2945Order of template parameters in optional comparisonsAlbuquerqueComplete
2948unique_ptr does not define operator<< for stream outputAlbuquerqueComplete
2950std::byte operations are misspecifiedAlbuquerqueComplete
2952iterator_traits should work for pointers to cv TAlbuquerqueComplete
2953LWG 2853 should apply to deque::erase tooAlbuquerque
2958Moves improperly defined as deletedAlbuquerque
2964Apparently redundant requirement for dynamic_pointer_castAlbuquerque
2965Non-existing path::native_string() in filesystem_error::what() specificationAlbuquerque
2972What is is_trivially_destructible_v<int>?AlbuquerqueComplete
2976Dangling uses_allocator specialization for packaged_taskAlbuquerqueComplete
2977unordered_meow::merge() has incorrect Throws: clauseAlbuquerque
2978Hash support for pmr::string and friendsAlbuquerque
2979aligned_union should require complete object typesAlbuquerqueComplete
2980Cannot compare_exchange empty pointersAlbuquerque
2981Remove redundant deduction guides from standard libraryAlbuquerque
2982Making size_type consistent in associative container deduction guidesAlbuquerque
2988Clause 32 cleanup missed one typenameAlbuquerque
2993reference_wrapper conversion from T&&Albuquerque
2998Requirements on function objects passed to {forward_,}list-specific algorithmsAlbuquerqueNothing to do
3001weak_ptr::element_type needs remove_extent_tAlbuquerque
3024variant's copies must be deleted instead of disabled via SFINAEAlbuquerque
2164What are the semantics of vector.emplace(vector.begin(), vector.back())?Jacksonville
2243istream::putback problemJacksonvilleComplete
2816resize_file has impossible postconditionJacksonvilleNothing to do
2843Unclear behavior of std::pmr::memory_resource::do_allocate()Jacksonville
2849Why does !is_regular_file(from) cause copy_file to report a "file already exists" error?JacksonvilleNothing to do
2851std::filesystem enum classes are now underspecifiedJacksonvilleNothing to do
2946LWG 2758's resolution missed further correctionsJacksonville
2969polymorphic_allocator::construct() shouldn't pass resource()Jacksonville
2975Missing case for pair construction in scoped and polymorphic allocatorsJacksonville
2989path's stream insertion operator lets you insert everything under the sunJacksonvilleCompleted
3000monotonic_memory_resource::do_is_equal uses dynamic_cast unnecessarilyJacksonville
3002[networking.ts] basic_socket_acceptor::is_open() isn't noexceptJacksonville
3004§[string.capacity] and §[vector.capacity] should specify time complexity for capacity()JacksonvilleNothing to do
3005Destruction order of arrays by make_shared/allocate_shared only recommended?Jacksonville
3007allocate_shared should rebind allocator to cv-unqualified value_type for constructionJacksonville
3009Including <string_view> doesn't provide std::size/empty/dataJacksonvilleComplete
3010[networking.ts] uses_executor says "if a type T::executor_type exists"Jacksonville
3013(recursive_)directory_iterator construction and traversal should not be noexceptJacksonvilleComplete
3014More noexcept issues with filesystem operationsJacksonvilleComplete
3015copy_options::unspecified underspecifiedJacksonvilleNothing to do
3017list splice functions should use addressofJacksonville
3020[networking.ts] Remove spurious nested value_type buffer sequence requirementJacksonville
3026filesystem::weakly_canonical still defined in terms of canonical(p, base)JacksonvilleComplete
3030Who shall meet the requirements of try_lock?JacksonvilleNothing to do
3034P0767R1 breaks previously-standard-layout typesJacksonvilleComplete
3035std::allocator's constructors should be constexprJacksonvilleComplete
3039Unnecessary decay in thread and packaged_taskJacksonvilleComplete
3041Unnecessary decay in reference_wrapperJacksonvilleComplete
3042is_literal_type_v should be inlineJacksonvilleComplete
3043Bogus postcondition for filesystem_error constructorJacksonville
3045atomic<floating-point> doesn't have value_type or difference_typeJacksonville
3048transform_reduce(exec, first1, last1, first2, init) discards execution policyJacksonville
3051Floating point classifications were inadvertently changed in P0175JacksonvilleNothing to do
3075basic_string needs deduction guides from basic_string_viewJacksonville

Last Updated: 5-Apr-2018