C++23

In the absence of face-to-face WG21 meetings, few new features have so far been added to the C++23 draft. But the following were added after the virtual WG21 meeting of 9 November 2020, where they were approved by straw polls:[7]

• Literal suffixes for std::size_t and the corresponding signed type[8]
• A member function contains for std::basic_string and std::basic_string_view, to check whether or not the string contains a given substring or character[9]
• A stacktrace library (<stacktrace>), based on Boost.Stacktrace[10]
• A type trait std::is_scoped_enum[11]
• The header <stdatomic.h>, for interoperability with C atomics[12]

After the virtual WG21 meeting of 22 February 2021, following features are added where they were approved by straw polls:[13]

• Repairing input range adaptors and counted_iterator.[14]
• Removing unnecessary empty parameter list () from lambda expressions.[15]
• Relax the requirements for time_point::clock.[16]
• std::visit for classes that are derived from std::variant.[17]
• Locks lock lockables.[18]
• Conditionally borrowed ranges.[19]
• std::to_underlying.[20]

After the Summer 2021 ISO C++ standards plenary virtual meeting of June 2021, new features and defect reports were approved by straw polls:[21]

• Consteval if (if consteval).[22]
• Narrowing contextual conversions to bool.[23]
• Allowing duplicate attributes.[24]
• std::span-based string-stream (<spanstream>).[25]
• std::out_ptr() and std::inout_ptr().[26]
• constexpr for std::optional, std::variant,[27] and std::type_info::operator==.[28]
• Iterators pair constructors for std::stack (stack) and std::queue (queue).[29]
• Few changes of the ranges library:
  • Generalized starts_with and ends_with for arbitrary ranges.[30]
  • Renamed split_view to lazy_split_view and new split_view.[31]
  • Relaxing the constraint on join_view.[32]
  • Removing default_initializable constraint from concept view.[33]
  • Range constructor for std::basic_string_view.[34]
• Prohibiting std::basic_string and std::basic_string_view construction from nullptr.[35]
• std::invoke_r.[36]
• Improvements on std::format.[37]
• Adding default arguments for std::pair's forwarding constructor.[38]

After the Autumn 2021 ISO C++ standards plenary virtual meeting of October 2021, new features and defect reports were approved by straw polls:[39]

• Non-literal variables, labels, and gotos in constexpr functions, but still ill-formed to evaluate them at compile-time.[40]
• Explicit this object parameter.[41]
• Changes on character sets and encodings.[42][43]
• New preprocessors: #elifdef and #elifndef.[44]
• Allowing alias declarations in init-statement.[45]
• Overloading multidimensional subscript operator (e.g. arr[1, 2]).[46]
• Decay copy in language: auto(x) or auto{x<nowiki>}</nowiki>.[47]
• Changes in text formatting library:
  • Fixing locale handling in chrono formatters.[48]
  • Use of forwarding references in format arguments to allow std::generator-like types.[49]
• Addition of type alias std::pmr::stacktrace which is equivalent to std::basic_stacktrace<std::pmr::polymorphic_allocator>.[50]
• Changes in ranges library:
  • Refined definition of a view.[51]
  • Replacing function template std::ranges::istream_view with alias templates std::ranges::istream_view, std::ranges::wistream_view, and customization point object std::views::istream.[52]
  • zip range adaptor family:[53]
    • zip_view
    • zip_transform_view
    • adjacent_view (and std::views::pairwise being equivalent to std::views::adjacent<2>)
    • adjacent_transform_view (and std::views::pairwise_transform being equivalent to std::views::adjacent_transform<2>)
• std::move_only_function.[54]
• Monadic operations for std::optional.[55]
• Member function template std::basic_string::resize_and_overwrite.[56]
• Printing volatile pointers (volatile T*).[57]
• std::byteswap.[58]
• Heterogeneous erasure overloads for associative containers.[59]
• Every specialization of std::span and std::basic_string_view is trivially copyable.[60]
• Adding conditional noexcept specifications to std::exchange.[61]
• Revamped specification and use of integer-class types.[62]
• Moving the deprecation of C headers to the main standard for interoperability with C.[63]

After the virtual WG21 meeting of 07 February 2022, the following features are added where they were approved by straw polls:[64]

• std::expected[65]
• constexpr for cmath and cstdlib[66]
• Function to mark unreachable code[67]
• ranges::to[68]
• Deprecate std::aligned_storage and std::aligned_union[69]
• A type trait to detect reference binding to temporary[70]
• Making std::unique_ptr constexpr[71]
• Pipe support for user-defined range adaptors[72]
• ranges::iota, ranges::shift_left and ranges::shift_right[73]
• views::join_with[74]
• Windowing range adaptors: views::chunk and views::slide[75]
• views::chunk_by[76]

• Garbage collection support.[77]