C++23

The current revision of the C++ standard.

New language features

• New language feature testing macros
• Explicit object parameter, explicit object member functions, a.k.a. "deducing this" (P0847R7)
• Multidimensional subscript operator (e.g. v[1, 3, 7] = 42;) (P2128R6)
• static operator[] (P2589R1), static operator(), and static lambdas (P1169R4)
• auto(x) and auto{x}: decay-copy in the language (P0849R8)
• Assumptions via new attribute [[assume(expression)]] (P1774R8)
• Attributes on lambda-expressions (P2173R1)
• Optional extended floating-point types: std::float{16|32|64|128}_t, and std::bfloat16_t (P1467R9)
• New preprocessor directives: #elifdef, #elifndef (P2334R1), and #warning (P2437R1)
• Literal suffix 'Z'/'z' for (signed) std::size_t literals (P0330R8), e.g. auto ouz = 0uz;
• White-spaces trimming before line splicing. (P2223R2)
• Simpler implicit move (P2266R3)
• Extending the lifetime of temporaries in range-based for loop initializer (P2718R0)
• CTAD from inherited constructors (P2582R1)
• Labels at the end of compound statements (P2324R2), e.g.
  

• Alias declarations (using) in init-statements (P2360R0), e.g.
  

• Make () more optional for lambda expressions (P1102R2)
• Narrowing contextual conversions to bool in static_assert and ifconstexpr (P1401R5)
• Make declaration order layout (of non-static class data members) mandated (P1847R4)
• Text encoding changes:
  • Character sets and encodings (P2314R4)
  • Consistent character literal encoding (P2316R2)
  • Named universal character escapes, e.g. "\N{CAT FACE}" for "🐱" (P2071R2)
  • Delimited escape sequences, e.g. "\o{7777}", "\x{C0DE}", "\u{CAFE}" (P2290R3)
  • Support for UTF-8 as a portable source file encoding (P2295R6)
• if consteval / if not consteval (P1938R3)
• constexpr changes:
  • Non-literal variables, labels, and gotos in constexpr functions (P2242R3)
  • Permitting static and thread_local variables in constant expressions in constexpr functions (P2647R1)
  • constexpr function does not need its return type and parameter types to be literal type (P2448R2)
  • constexpr function for which no invocation satisfies the requirements of a core constant expression (P2448R2)

New library features

• New library feature testing macros

New modules

• std and std.compat (P2465R3)

New headers

• <expected>
• <flat_map>
• <flat_set>
• <generator>
• <mdspan>
• <print>
• <spanstream>
• <stacktrace>
• <stdfloat>

C compatibility headers:

• <stdatomic.h> (P0943R6)

Library features

General Utilities

• std::expected: a new vocabulary type to return a function's result (<expected>) (P0323R12, P2549R1)
• std::move_only_function: a move-only callable wrapper (P0288R9)
• std::bind_back: a call wrapper (P2387R3)
• std::byteswap: reverses the bytes (P1272R4)
• std::forward_like (P2445R1)
• std::invoke_r: invokes a Callable object (P2136R3)
• std::to_underlying: a utility function to get the underlying value of enum (P1682R3)
• std::unreachable: a function to mark unreachable code (P0627R6)
• Monadic operations (transform, or_else, and and_then) for std::optional (P0798R8) and std::expected (P2505R5)
• std::tuple is compatible with other tuple-like objects (P2165R4)
• Adding default arguments for std::pair's forwarding constructor (P2718R0)
• std::basic_common_reference specialization for std::reference_wrapper yielding reference types (P2655R3)

Coroutine Library

• std::generator: synchronous coroutine generator for ranges (P2502R2, P2787R0)

Diagnostic

• Stacktrace library (P0881R7)

Algorithm, Iterators, and Ranges

• New range adaptors:
  • views::adjacent and views::adjacent_transform (P2321R2)
  • views::as_const (P2278R4)
  • views::as_rvalue (P2446R2)
  • views::cartesian_product (P2374R4)
  • views::chunk_by (P2443R1)
  • views::chunk (P2442R1)
  • views::enumerate (P2164R9)
  • views::join_with (P2441R2)
  • views::repeat (P2474R2)
  • views::slide (P2442R1)
  • views::stride (P1899R3)
  • views::zip, views::zip_transform (P2321R2)
• ranges::range_adaptor_closure: a helper for program-defined range adaptor closures (P2387R3)
• ranges::to: a range conversion function (P1206R7)
• New constrained ranges algorithm:
  • ranges::starts_with and ranges::ends_with (P1659R3)
  • ranges::contains and ranges::contains_subrange (P2302R4)
  • ranges::find_last, ranges::find_last_if, and ranges::find_last_if_not (P1223R5)
  • ranges::iota, ranges::shift_left, and ranges::shift_right: rangified versions of non-constrained algorithms (P2440R1)
  • ranges::fold_left etc.: range fold algorithms (P2322R6)
• Rectifying constant iterators, sentinels, and ranges, that is, ranges::cbegin and other similar utilities returning constant iterators should be fully guaranteed even for shallow-const views (such as std::span) (P2278R4)
• Making multi-param constructors of some views explicit (P2711R1)
• Ranges iterators as inputs to non-ranges algorithms (P2408R5)
• Relaxing range adaptors to allow for move-only types (P2494R2)

Containers

• std::mdspan: a non-owning multidimensional array reference (P0009R18, P2599R2, P2604R0, P2613R1, P2763R1)
• Constructibility and assignability of containers from other compatible ranges (P1206R7)
• std::flat_set, std::flat_multiset (P1222R4), std::flat_map, std::flat_multimap (P0429R9): flat sets and flat maps - container adaptors wrapping underlying sorted random-access containers
• Allowing iterator pair construction in std::stack and std::queue (P1425R4)
• Heterogeneous erasure overloads for associative containers (P2077R2)
• Non-deduction context for allocators in container deduction guides (P1518R2)
• Requiring std::span and std::basic_string_view to be trivially copyable (P2251R1)

Compile-time support

• constexpr support for:
  • std::bitset (P2417R2)
  • std::unique_ptr (P2273R3)
  • std::type_info::operator== (P1328R1)
  • Some <cmath> functions (P0533R9)
  • Integral overloads of std::to_chars and std::from_chars (P2291R3)
• Metaprogramming utilities:
  • Adding move-only types support for comparison concepts (P2404R3)
  • Type traits:
    • std::is_scoped_enum (P1048R1)
    • std::is_implicit_lifetime (P2674R1)
    • std::reference_constructs_from_temporary, and std::reference_converts_from_temporary (P2255R2)

Memory Management

• std::out_ptr and std::inout_ptr: smart pointer adaptors for C interoperability (P1132R7)
• std::allocate_at_least and std::allocator::allocate_at_least (P0401R6)
• std::start_lifetime_as: an explicit lifetime management function for implicit-lifetime types (P2590R2)
• Disallowing user specialization of std::allocator_traits (P2652R2)

String and Text Processing

• New member functions and changes in string types:
  • std::basic_string::contains and std::basic_string_view::contains (P1679R3)
  • Disabling construction from nullptr for std::basic_string and std::basic_string_view (P2166R1)
  • Explicit range constructor for std::basic_string_view (P1989R2)
  • std::basic_string::resize_and_overwrite (P1072R10)
  • Rvalue reference overload of std::basic_string::substr for efficient slicing (P2438R2)
• Formatting ranges, tuples, escaped presentation of characters and strings, std::thread::id, and stacktraces. (P2286R8) (P2585R1) (P2693R1)

I/O and print

• Formatted output functions std::print and std::println provided in header <print> (P2093R14)
• spanstream library (std::span-based string stream) provided in header <spanstream> (P0448R4)
• Support exclusive mode in std::fstreams (P2467R1)
• Support of printing volatile T*: std::basic_ostream::operator<<(const volatile void*) (P1147R1)

Obsolete features

Removed features

• Garbage collection support and reachability-based leak detection. (P2186R2)
• Mixed wide string literals concatenation support, e.g., const auto* no = u"q" U"p" is ill-formed. (P2201R1)
• Non-encodable wide character literals and multicharacter wide character literals, e.g. wchar_t x = 'db' is ill-formed. (P2362R3)

Deprecated features

• std::aligned_storage and std::aligned_union (P1413R3)
• std::numeric_limits::has_denorm (P2614R2)

Reverted deprecations

• The operator, (comma operator) in subscript expressions (but the semantics has been changed to support overloadable multidimensional subscript operator[]).
• Some C headers (the corresponding <*.h> headers for compatibility with C) (P2340R1)

Defect reports

Compiler support

Main Article: C++23 compiler support

C++23 core language features

C++23 library features

* - hover over a cell marked with the star * to see additional pop-up notes.
DRnn - the number nn after "DR" denotes target C++ revision the Defect Report is applied to, e.g., DR20 → C++20.

External links