C++26
Computer programming language
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C++26 is the informal name for the version of the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) 14882 standard for the C++ programming language that follows C++23. The current working draft of this version is N5032.[1] Papers proposed and adopted into the standard by the C++ Standards Committee and minutes of the standardization meeting held at Sofia, Bulgaria and online in June 2025 are publicly available.[2] The draft wording is feature complete,[3] and is being sent out for international comment ballot.[4] After resolving some ballot comments at the November 2025 standardization meeting in Kona, Hawaii, the C++ Standards Committee is expected to finish resolving ballot comments, technically finalize the draft, and send the draft out for final approval ballot at the following standardization meeting[3] in London, United Kingdom in March 23 to 28, 2026.[5][6]
Experimental and standard compilers implementing some of the upcoming features can be tried on short code snippets through the Compiler Explorer. Some of the compiler variants are distinguished only by the short identifiers of papers proposing the new features they implement, such as "P3372" for constexpr containers and adaptors.
Features
Changes that have been accepted into C++26 include:
Language
- Compile-time reflection.[7] (An experimental fork of Clang by Dan Katz, as well as GCC 16, implement these features. These compilers as well as another implementation from EDG can all be tried through the Compiler Explorer.) This uses a new operator
^^(colloquially called the "cat-ears operator"[8]) for invoking reflection, rather than the Reflection TS keywordreflexpr. - Support for annotations to be used in reflection which behave differently from the existing attribute system used by the compiler.[9] See also Java annotations.
- Contracts[10] adding keyword
contract_assert, and additionally identifiers with special meaning,preandpost.[11] (An experimental fork of Clang by Eric W Fiselier and a few GCC variants supporting contracts are available through the Compiler Explorer.) - User-generated
static_assertmessages[12] - Introduction of erroneous behaviour for reading uninitialized variables [13]
[[indeterminate]]attribute [14]- Deleting a pointer to an incomplete type should be ill-formed
- Removing deprecated array comparisons
constexprstructured bindings and references toconstexprvariablesconstexprplacementnewconstexprcast fromvoid*constexprcontainers and adaptors [15]- Variadic friends
- Allowing exception throwing in constant-evaluation
- Placeholder variables with no name
- Ordering of constraints involving fold expressions
- Pack indexing
- Structured bindings can introduce a pack
- Attributes for structured bindings
- Structured binding declaration as a condition
- Adds
#embeddirective (first introduced in C23) for binary resource inclusion and__has_embedallowing the availability of a resource to be checked by preprocessor directives - Unevaluated strings
- Adding
@,$, and`to the basic character set. While currently unused, this would allow those characters to be given potential use in the future. = delete("reason");, deleting compiler-generated methods with a specified reason- Oxford variadic comma, i.e. "Deprecate ellipsis parameters without a preceding comma. The syntax
(int...)is incompatible with C, detrimental to C++, and easily replaceable with(int, ...)."[16] - Forbidding returning reference to a temporary variable in a function [17]
Library
<meta>: Compile-time reflection support<contracts>: Design-by-contract support- Bounds-hardened standard library[18]
- Parallel scheduler providing a standard async execution context that guarantees forward progress[19]
<simd>: Data-parallel access (Single instruction, multiple data or SIMD) support- Async sender/receiver model for structured concurrency[20] (Libunifex is a prototype implementation that can be compiled in C++17 or later.)
<hazard_pointer>: Hazard pointers for threadingstd::copyable_functionstd::is_within_lifetime<hive>: Hive data structure support which reuses erased elements' memory (similar to an object pool). It is based onplf::colony.<rcu>: Support for safe reclamation read-copy-update mechanism<inplace_vector>: In-place vector data structure support, which is a resizable, fixed capacity, inplace contiguous arraystd::submdspan()- Native handles in file streams
std::formatter<std::filesystem::path>- Interfacing string streams with
std::string_view - Interfacing
std::bitsetwithstd::string_view std::views::concat- Concatenation of strings and string views
<text_encoding>: Support for accessing the IANA Character Sets registry- Printing blank lines with
std::println() std::ranges::generate_random<linalg>: A free function linear algebra interface based on the BLAS- Hashing support for
std::chronovalue classes - Added tuple protocol to
std::complex - More
constexprfor<cmath>and<complex> - Adding the new 2022 SI prefixes on ratios:
std::quecto,std::ronto,std::ronna, andstd::quetta - Saturation arithmetic with, among others,
std::add_sat,std::div_sat <debugging>: Debugging support and language features to aid debugger programs<execution>expanded with an "execution control library" for asynchronous operations and coroutines, including astd::execution::taskclass[21]
Reception
Several people issued trip reports from the Sofia C++ Standards Committee meeting at which the draft became feature complete,[19][22] and from the International C++ Conference, C++ On Sea, immediately afterward.[23]
All highlighted the introduction of compile-time reflection in particular as a major change. In particular, Herb Sutter, chair of the ISO C++ Standards Committee and Hana Dusíková, assistant chair of the "Language Evolution" working group of the C++ Standards Committee, described the potential impacts for including reflection to C++ as a "whole new language."[19]
The contracts feature for C++26 has been criticised by some in the C++ committee, for varying reasons.[24]
The trivial relocatability feature, which proposed the new identifiers/class property specifiers trivially_relocatable_if_eligible and replaceable_if_eligible[25], was removed from C++26 due to implementation bugs and deferred to a later standard.[26]