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 | Complete | 14.0 |
| 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 | Complete | 14.0 |
| 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 | Complete | 14.0 |
| 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 | ||