C++26
Revision of the C++ programming language released in 2026
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C++26 is the informal name for the open standard revision of the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) 14882 standard for the C++ programming language that follows C++23, officially shipped by WG21 on 28 March 2026.[1][2] The current working revision of C++26 is N5046.[3]
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.[4] The draft wording is feature complete,[5] and is being sent out for international comment ballot.[6] After resolving some ballot comments at the November 2025 standardization meeting in Kona, Hawaii, the C++ Standards Committee finished expected resolving ballot comments, technically finalized the draft, and send the draft out for final approval ballot at the following standardization meeting[5] in London, United Kingdom from 23 to 28 of March 2026.[7][8]
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.
As of 30 April 2026, GCC supports most of the C++26 features beginning with GCC 16.1.[9][10]
As of 2026, C++26 is the next revision of the C++ programming language standard. ISO/IEC JTC 1/SC 22/WG21 is responsible for the standardization process. N5046 was the May 2026 working draft (replacing N5032); the Draft International Standard was not completed for ISO ballot at that time.[11]
The compiler implementations started supporting C++26 experimentally even before the standard was finalised. GCC has implemented some C++26 features with the flag -std=c++26, but is still experimental as the ISO C++26 standard was finalizing its standardization.[12]
Features
Changes that have been accepted into C++26 include:
Language
- Reflection, which runs at compile-time (unlike languages like Java and C#, which run at runtime).[13] (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 reflection operator
^^[14] (colloquially called the "cat-ears operator"[15]) which creates a mirror primitivestd::meta::info[16] (rather than the Reflection TS keywordreflexpr), which can be spliced back into source code using the[: :]splice specifiers.[17] - Annotations, which attach reflective metadata to an object (and are processed later than compiler attributes).[18]
- Contracts[19] adding keyword
contract_assert, and additionally identifiers with special meaning,preandpost.[20] (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,[21] which supportconstexprmessages rather than just unevaluated strings - Introduction of erroneous behaviour for reading uninitialized variables [22]
[[indeterminate]]attribute, which indicates that a variable or function parameter has an indeterminate value if not initialized[23][24]- Deprecate
std::memory_order::consumeandstd::kill_dependency(),[25][26] due to complicating the memory model[further explanation needed] and low compiler adoption[27] - Remove
[[carries_dependency]]attribute, due to the deprecation ofstd::memory_order::consume[28] - Deleting a pointer to an incomplete type should be ill-formed
- Removing deprecated array comparisons
- Various constexpr improvements:
- Variadic friends
- Oxford variadic comma, i.e. "Deprecate ellipsis parameters without a preceding comma." For example, the syntax
void f(int a...);is incompatible with C, detrimental to C++,[further explanation needed] and easily replaceable withvoid f(int a, ...);.[32] - Placeholder variables with no name[33]
- 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. - Disabling special member functions with a specified reason (
= delete("Deletion reason here");) - Forbidding returning reference to a temporary variable in a function [34]
template forcompile-time loops (a.k.a. expansion statements)[35] to iterate over type/parameter packs, tuple-like objects and meta-objects.[36]- Allow attaching the entry point,
main, to the global module. This allows themain()function to haveextern "C++"linkage.[37]
Library
- New standard library headers and namespaces:
<contracts>: Contracts support, and namespacestd::contracts<debugging>: Debugging support and language features to aid debugger programs[38]<hazard_pointer>: Hazard pointers for threading[39]<hive>: Hive data structure support which reuses erased elements' memory (similar to an object pool). It is based onplf::colony.[40]<inplace_vector>: In-place vector data structure support, which is a resizable, fixed capacity, inplace contiguous array[41]<linalg>: A free function linear algebra interface based on the BLAS, and namespacestd::linalg[42]<meta>: Compile-time reflection support, and namespacestd::meta<rcu>: Support for safe reclamation read-copy-update mechanism[43]<simd>: Data-parallel access (Single instruction, multiple data or SIMD) support, and namespacestd::simd[44]<text_encoding>: Support for accessing the IANA Character Sets registry
- Parallel scheduler (in
<execution>) providing a standard asynchronous execution context that guarantees forward progress,[45] with the "execution control library" for asynchronous operations and coroutines in namespacestd::execution,[46] including a "sender" abstraction and a designatedstd::execution::task<T, Env>class.[47] It was proposed based on Meta's libunifex framework, and later Nvidia's stdexec framework.[48][49] - "Hardened" standard library, which includes bounds checking and turns instances of undefined behavior into contract violations[50][51][52]
std::copyable_function, general-purpose polymorphic function wrapper which may be copy-constructed and copy-assignedstd::is_within_lifetime, determines if a pointer points to an object that is within its lifetimestd::submdspan(), returns a view of a subset of an existingstd::mdspan- Native handles in file streams
- Support for
std::optional<T&>, an optional storing a reference[53] - Specialization of
std::formatter<>forstd::filesystem::path(std::formatter<std::filesystem::path>) - Interfacing string streams with
std::string_view - Interfacing
std::bitsetwithstd::string_view std::views::concat, a view for concatenation of other views- Concatenation of strings and string views
- Printing blank lines with
std::println()(already implemented in C++23 by most compiler vendors) std::ranges::generate_random, fills a range with random numbers from a uniform random bit generator- 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:
std::saturating_add,std::saturating_sub,std::saturating_mul,std::saturating_divandstd::saturating_cast
Reception
Several people issued trip reports from the Sofia C++ Standards Committee meeting at which the draft became feature complete,[45][54] and from the International C++ Conference, C++ On Sea, immediately afterward.[55]
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 C++ reflection as a "whole new language."[45] Sutter further described C++26 as the most 'compelling' release since C++11.[2]
The contracts feature was criticised by some in the C++ committee, for varying reasons (such as questioning its safety, complexity, or implementation details).[56]
The trivial relocatability feature, which proposed new specifiers trivially_relocatable_if_eligible and replaceable_if_eligible,[20] was removed from C++26 due to implementation bugs and deferred to a later standard.[57]