<p>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).</p>
<p>This page shows the status of libc++; the status of clang's support of the language features is <ahref="https://clang.llvm.org/cxx_status.html#cxx2a">here</a>.</p>
<tr><td><ahref="https://wg21.link/n3346">3346</a></td><td>LWG</td><td>Terminology for Container Element Requirements - Rev 1</td><td>Kona</td><td>Complete</td><td>3.4</td></tr>
<tr><td><ahref="https://wg21.link/P0674R1">P0674R1</a></td><td>LWG</td><td>Extending make_shared to Support Arrays</td><td>Toronto</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0202R3">P0202R3</a></td><td>LWG</td><td>Add constexpr modifiers to functions in <algorithm> and <utility> Headers</td><td>Albuquerque</td><td><I>In Progress</I></td><td>7.0</td></tr>
<tr><td><ahref="https://wg21.link/P0415R1">P0415R1</a></td><td>LWG</td><td>Constexpr for <tt>std::complex</tt></td><td>Albuquerque</td><td><I>In Progress</I></td><td>7.0</td></tr>
<tr><td><ahref="https://wg21.link/P0439R0">P0439R0</a></td><td>LWG</td><td>Make <tt>std::memory_order</tt> a scoped enumeration</td><td>Albuquerque</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0457R2">P0457R2</a></td><td>LWG</td><td>String Prefix and Suffix Checking</td><td>Albuquerque</td><td>Complete</td><td>6.0</td></tr>
<tr><td><ahref="https://wg21.link/P0600R1">P0600R1</a></td><td>LWG</td><td>nodiscard in the Library</td><td>Albuquerque</td><td><I>In Progress</I></td><td>7.0</td></tr>
<tr><td><ahref="https://wg21.link/P0653R2">P0653R2</a></td><td>LWG</td><td>Utility to convert a pointer to a raw pointer</td><td>Albuquerque</td><td>Complete</td><td>6.0</td></tr>
<tr><td><ahref="https://wg21.link/P0768R1">P0768R1</a></td><td>CWG</td><td>Library Support for the Spaceship (Comparison) Operator</td><td>Albuquerque</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0355R7">P0355R7</a></td><td>LWG</td><td>Extending chrono to Calendars and Time Zones</td><td>Jacksonville</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0551R3">P0551R3</a></td><td>LWG</td><td>Thou Shalt Not Specialize <tt>std</tt> Function Templates!</td><td>Jacksonville</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0753R2">P0753R2</a></td><td>LWG</td><td>Manipulators for C++ Synchronized Buffered Ostream</td><td>Jacksonville</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0905R1">P0905R1</a></td><td>CWG</td><td>Symmetry for spaceship</td><td>Jacksonville</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0966R1">P0966R1</a></td><td>LWG</td><td><tt>string::reserve</tt> Should Not Shrink</td><td>Jacksonville</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0458R2">P0458R2</a></td><td>LWG</td><td>Checking for Existence of an Element in Associative Containers</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0475R1">P0475R1</a></td><td>LWG</td><td>LWG 2511: guaranteed copy elision for piecewise construction</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0528R3">P0528R3</a></td><td>CWG</td><td>The Curious Case of Padding Bits, Featuring Atomic Compare-and-Exchange</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0542R5">P0542R5</a></td><td>CWG</td><td>Support for contract based programming in C++</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0619R4">P0619R4</a></td><td>LWG</td><td>Reviewing Deprecated Facilities of C++17 for C++20</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0646R1">P0646R1</a></td><td>LWG</td><td>Improving the Return Value of Erase-Like Algorithms</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0722R3">P0722R3</a></td><td>CWG</td><td>Efficient sized delete for variable sized classes</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0758R1">P0758R1</a></td><td>LWG</td><td>Implicit conversion traits and utility functions</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0769R2">P0769R2</a></td><td>LWG</td><td>Add shift to <algorithm></td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0788R3">P0788R3</a></td><td>LWG</td><td>Standard Library Specification in a Concepts and Contracts World</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0879R0">P0879R0</a></td><td>LWG</td><td>Constexpr for swap and swap related functions Also resolves LWG issue 2800.</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0935R0">P0935R0</a></td><td>LWG</td><td>Eradicating unnecessarily explicit default constructors from the standard library</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P0941R2">P0941R2</a></td><td>CWG</td><td>Integrating feature-test macros into the C++ WD</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P1023R0">P1023R0</a></td><td>LWG</td><td>constexpr comparison operators for std::array</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P1025R1">P1025R1</a></td><td>CWG</td><td>Update The Reference To The Unicode Standard</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td><ahref="https://wg21.link/P1120R0">P1120R0</a></td><td>CWG</td><td>Consistency improvements for <=> and other comparison operators</td><td>Rapperswil</td><td></td><td></td></tr>
<p>The missing bits in P0600 are in [mem.res.class], [mem.poly.allocator.class], and [container.node.overview]</p>
<p>The missing bits in P0202 are in <tt>copy</tt>, <tt>copy_backwards</tt>, <tt>move</tt>, and <tt>move_backwards</tt> (and the ones that call them: <tt>copy_n</tt>, <tt>rotate_copy</tt>, <tt>merge</tt>, <tt>set_union</tt>, <tt>set_difference</tt>, and <tt>set_symmetric_difference</tt>). This is because the first four algorithms have specializations that call <tt>memmove</tt> which is not constexpr. See <ahref="https://bugs.llvm.org/show_bug.cgi?id=25165">Bug 25165</a></p>
<tr><td><ahref="https://wg21.link/LWG2070">2070</a></td><td><tt>allocate_shared</tt> should use <tt>allocator_traits<A>::construct</tt></td><td>Toronto</td><td>Resolved by <ahref="https://wg21.link/P0674R1">P0674R1</a></td></tr>
<tr><td><ahref="https://wg21.link/LWG2444">2444</a></td><td>Inconsistent complexity for <tt>std::sort_heap</tt></td><td>Toronto</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2593">2593</a></td><td>Moved-from state of Allocators</td><td>Toronto</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2597">2597</a></td><td><tt>std::log</tt> misspecified for complex numbers</td><td>Toronto</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2783">2783</a></td><td><tt>stack::emplace()</tt> and <tt>queue::emplace()</tt> should return <tt>decltype(auto)</tt></td><td>Toronto</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2932">2932</a></td><td>Constraints on parallel algorithm implementations are underspecified</td><td>Toronto</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2937">2937</a></td><td>Is <tt>equivalent("existing_thing", "not_existing_thing")</tt> an error</td><td>Toronto</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2940">2940</a></td><td><tt>result_of</tt> specification also needs a little cleanup</td><td>Toronto</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2954">2954</a></td><td>Specialization of the convenience variable templates should be prohibited</td><td>Toronto</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2961">2961</a></td><td>Bad postcondition for <tt>set_default_resource</tt></td><td>Toronto</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2966">2966</a></td><td>Incomplete resolution of US 74</td><td>Toronto</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG2974">2974</a></td><td>Diagnose out of bounds <tt>tuple_element/variant_alternative</tt></td><td>Toronto</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2870">2870</a></td><td>Default value of parameter theta of polar should be dependent</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2935">2935</a></td><td>What should create_directories do when p already exists but is not a directory?</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2941">2941</a></td><td>[thread.req.timing] wording should apply to both member and namespace-level functions</td><td>Albuquerque</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG2944">2944</a></td><td>LWG 2905 accidentally removed requirement that construction of the deleter doesn't throw an exception</td><td>Albuquerque</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG2945">2945</a></td><td>Order of template parameters in optional comparisons</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2948">2948</a></td><td>unique_ptr does not define operator<<forstreamoutput</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2952">2952</a></td><td>iterator_traits should work for pointers to cv T</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2953">2953</a></td><td>LWG 2853 should apply to deque::erase too</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2958">2958</a></td><td>Moves improperly defined as deleted</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2964">2964</a></td><td>Apparently redundant requirement for dynamic_pointer_cast</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2965">2965</a></td><td>Non-existing path::native_string() in filesystem_error::what() specification</td><td>Albuquerque</td><td>Nothing to do</td></tr>
<tr><td><ahref="https://wg21.link/LWG2972">2972</a></td><td>What is is_trivially_destructible_v<int>?</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2976">2976</a></td><td>Dangling uses_allocator specialization for packaged_task</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2977">2977</a></td><td>unordered_meow::merge() has incorrect Throws: clause</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2978">2978</a></td><td>Hash support for pmr::string and friends</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2979">2979</a></td><td>aligned_union should require complete object types</td><td>Albuquerque</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG2981">2981</a></td><td>Remove redundant deduction guides from standard library</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2982">2982</a></td><td>Making size_type consistent in associative container deduction guides</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2988">2988</a></td><td>Clause 32 cleanup missed one typename</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2993">2993</a></td><td>reference_wrapper<T> conversion from T&&</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2998">2998</a></td><td>Requirements on function objects passed to {forward_,}list-specific algorithms</td><td>Albuquerque</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3024">3024</a></td><td>variant's copies must be deleted instead of disabled via SFINAE</td><td>Albuquerque</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2164">2164</a></td><td>What are the semantics of <tt>vector.emplace(vector.begin(), vector.back())</tt>?</td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2816">2816</a></td><td><tt>resize_file</tt> has impossible postcondition</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG2843">2843</a></td><td>Unclear behavior of <tt>std::pmr::memory_resource::do_allocate()</tt></td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2849">2849</a></td><td>Why does <tt>!is_regular_file(from)</tt> cause <tt>copy_file</tt> to report a "file already exists" error?</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG2851">2851</a></td><td><tt>std::filesystem</tt> enum classes are now underspecified</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG2975">2975</a></td><td>Missing case for <tt>pair</tt> construction in scoped and polymorphic allocators</td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG2989">2989</a></td><td><tt>path</tt>'s stream insertion operator lets you insert everything under the sun</td><td>Jacksonville</td><td>Completed</td></tr>
<tr><td><ahref="https://wg21.link/LWG3004">3004</a></td><td>§[string.capacity] and §[vector.capacity] should specify time complexity for <tt>capacity()</tt></td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3005">3005</a></td><td>Destruction order of arrays by <tt>make_shared/allocate_shared</tt> only recommended?</td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3007">3007</a></td><td><tt>allocate_shared</tt> should rebind allocator to <i>cv</i>-unqualified <tt>value_type</tt> for construction</td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3009">3009</a></td><td>Including <tt><string_view></tt> doesn't provide <tt>std::size/empty/data</tt></td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3010">3010</a></td><td>[networking.ts] <tt>uses_executor</tt> says "if a type <tt>T::executor_type</tt> exists"</td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3013">3013</a></td><td><tt>(recursive_)directory_iterator</tt> construction and traversal should not be <tt>noexcept</tt></td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3014">3014</a></td><td>More <tt>noexcept</tt> issues with filesystem operations</td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3015">3015</a></td><td><tt>copy_options::<i>unspecified</i></tt> underspecified</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3017">3017</a></td><td><tt>list splice</tt> functions should use <tt>addressof</tt></td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3026">3026</a></td><td><tt>filesystem::weakly_canonical</tt> still defined in terms of <tt>canonical(p, base)</tt></td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3030">3030</a></td><td>Who shall meet the requirements of <tt>try_lock</tt>?</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3035">3035</a></td><td><tt>std::allocator</tt>'s constructors should be <tt>constexpr</tt></td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3039">3039</a></td><td>Unnecessary <tt>decay</tt> in <tt>thread</tt> and <tt>packaged_task</tt></td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3041">3041</a></td><td>Unnecessary <tt>decay</tt> in <tt>reference_wrapper</tt></td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3042">3042</a></td><td><tt>is_literal_type_v</tt> should be inline</td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3043">3043</a></td><td>Bogus postcondition for <tt>filesystem_error</tt> constructor</td><td>Jacksonville</td><td>Complete</td></tr>
<tr><td><ahref="https://wg21.link/LWG3045">3045</a></td><td><tt>atomic<<i>floating-point</i>></tt> doesn't have <tt>value_type</tt> or <tt>difference_type</tt></td><td>Jacksonville</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3051">3051</a></td><td>Floating point classifications were inadvertently changed in P0175</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3062">3062</a></td><td>Unnecessary decay_t in is_execution_policy_v should be remove_cvref_t</td><td>Rapperswil</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3067">3067</a></td><td>recursive_directory_iterator::pop must invalidate</td><td>Rapperswil</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3071">3071</a></td><td>[networking.ts] read_until still refers to "input sequence"</td><td>Rapperswil</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3074">3074</a></td><td>Non-member functions for valarray should only deduce from the valarray</td><td>Rapperswil</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3079">3079</a></td><td>LWG 2935 forgot to fix the existing_p overloads of create_directory</td><td>Rapperswil</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3080">3080</a></td><td>Floating point from_chars pattern specification breaks round-tripping</td><td>Rapperswil</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3083">3083</a></td><td>What should ios::iword(-1) do?</td><td>Rapperswil</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3094">3094</a></td><td>[time.duration.io]p4 makes surprising claims about encoding</td><td>Rapperswil</td><td></td></tr>
<tr><td><ahref="https://wg21.link/LWG3100">3100</a></td><td>Unnecessary and confusing "empty span" wording</td><td>Rapperswil</td><td><i>Nothing to do</i></td></tr>
<tr><td><ahref="https://wg21.link/LWG3102">3102</a></td><td>Clarify span iterator and const_iterator behavior</td><td>Rapperswil</td><td></td></tr>
