---

features:

- desc: "UB? In My Lexer? (Remove undefined behavior from lexing)"

paper: P2621

support:

- GCC

- Clang 3.3

- Xcode 16

- desc: "Making non-encodable string literals ill-formed"

paper: P1854

support:

- GCC 14

- Clang 14

- Xcode 16

- desc: "[Unevaluated strings](https://cppreference.com/cpp/language/string_literal#Unevaluated_strings)"

paper: P2361

support:

- GCC 14

- tool: Clang 17

status: partial

note: "Attributes arguments don't yet parse as unevaluated string literals."

- Clang 18

- Xcode 16

- desc: "Add @, $, and ` to the [basic character set](https://cppreference.com/cpp/language/charset#Basic_character_set)"

paper: P2558

support:

- GCC 15

- Clang

- Xcode 15

- desc: "`constexpr` cast from `void*`: towards `constexpr` type-erasure"

paper: P2738

summary: "Recover a typed pointer from `void*` during constant evaluation."

support:

- GCC 14

- Clang 17

- Xcode 16.3

- R++

ftm:

- name: __cpp_constexpr

value: 202306L

content: constexpr-void-cast.md

- desc: "On the ignorability of standard attributes"

paper: P2552

support:

- GCC 15

- Clang

- Xcode 16.3

- desc: "Static storage for braced initializers"

paper: P2752

support: [GCC 14, R++]

- desc: "User-generated `static_assert` messages"

paper: P2741

content: static-assert-message.md

summary: "`static_assert` can now use user-generated strings, not just string literals."

support:

- GCC 14

- Clang 17

- Xcode 16.3

- tool: R++

status: unsupported

issue: RSCPP-35928

ftm:

- name: __cpp_static_assert

value: 202306L

- desc: "A nice placeholder with no name (using `_` as a variable name)"

paper: P2169

summary: "The underscore `_` can now be used as a placeholder variable name that doesn't actually bind a name."

support:

- GCC 14

- Clang 18

- Xcode 16.3

- R++ 2025.2

ftm:

- name: __cpp_placeholder_variables

value: 202306L

content: placeholder-variable.md

- desc: "Testing for success or failure of `<charconv>` functions"

lib: true

paper: P2497

support: [GCC 14, Clang 18]

ftm:

- name: __cpp_lib_to_chars

value: 202306L

- desc: "Hashing support for `chrono` value classes"

paper: P2592

lib: true

support: [GCC 16, Clang 22]

ftm:

- name: __cpp_lib_chrono

value: 202306L

- desc: "Arithmetic overloads of `std::to_string()` and `std::to_wstring()` use `std::format()`"

paper: P2587

lib: true

support: [GCC 14]

ftm:

- name: __cpp_lib_to_string

value: 202306L

- desc: "`constexpr` stable sorting"

paper: P2562

lib: true

support: [GCC 15, Clang 21, Xcode 26.4]

ftm:

- name: __cpp_lib_constexpr_algorithms

value: 202306L

- desc: "Read-copy update (RCU) (`<rcu>`)"

paper: P2545

summary: "RCU provides efficient concurrent reads with minimal synchronization."

lib: true

ftm:

- name: __cpp_lib_rcu

value: 202306L

- desc: "Hazard pointers (`<hazard_pointer>`)"

paper: P2530

summary: "Hazard pointers enable safe memory reclamation in lock-free data structures."

lib: true

ftm:

- name: __cpp_lib_hazard_pointer

value: 202306L

- desc: "ADL-proof `std::projected`"

paper: P2538

lib: true

support:

- GCC 14

- Clang 18

- MSVC 14.38

- Xcode 16

- desc: "Interfacing `std::stringstream` with `std::string_view`"

paper: P2495

lib: true

support:

- GCC 16

- Clang 19

- Xcode 16.3

ftm:

- name: __cpp_lib_sstream_from_string_view

value: 202306L

- desc: "Formatting pointers"

paper: P2510

content: formatting-pointers.md

lib: true

support:

- GCC 14

- Clang 17

- MSVC 14.40

ftm:

- name: __cpp_lib_format

value: 202304L

- desc: "Freestanding Feature-Test Macros and Implementation-Defined Extensions"

paper: P2198

lib: true

support: [MSVC 14.38]

ftm:

- name: __cpp_lib_freestanding_feature_test_macros

value: 202306L

- name: __cpp_lib_freestanding_functional

value: 202306L

- name: __cpp_lib_freestanding_iterator

value: 202306L

- name: __cpp_lib_freestanding_memory

value: 202306L

- name: __cpp_lib_freestanding_operator_new

value: 202306L

- name: __cpp_lib_freestanding_ranges

value: 202306L

- name: __cpp_lib_freestanding_ratio

value: 202306L

- name: __cpp_lib_freestanding_tuple

value: 202306L

- name: __cpp_lib_freestanding_utility

value: 202306L

- desc: "Freestanding `std::char_traits`, `std::errc` and facilities in: `<charconv>`, `<cstdlib>`, `<cstring>`, `<cwchar>`"

paper: P2338

lib: true

support: [MSVC 14.38]

ftm:

- name: __cpp_lib_freestanding_char_traits

value: 202306L

- name: __cpp_lib_freestanding_charconv

value: 202306L

- name: __cpp_lib_freestanding_cstdlib

value: 202306L

- name: __cpp_lib_freestanding_cstring

value: 202306L

- name: __cpp_lib_freestanding_cwchar

value: 202306L

- name: __cpp_lib_freestanding_errc

value: 202306L

- desc: "Freestanding language: Optional `::operator new`"

paper: P2013

lib: true

support: [MSVC 14.38]

- desc: "Atomic minimum/maximum"

paper: P0493

lib: true

support: [GCC 16, Clang 24]

ftm:

- name: __cpp_lib_atomic_min_max

value: 202403L

- desc: "Extending associative containers with the remaining heterogeneous overloads"

paper: P2363

lib: true

support: [GCC 16]

ftm:

- name: __cpp_lib_associative_heterogeneous_insertion

value: 202306L

keywords:

[

"insert",

"insert_or_assign",

"bucket",

"map",

"set",

"unordered",

"emplace",

"multiset",

"multimap",

]

- desc: "Enabling the use of `std::weak_ptr` as keys in unordered associative containers"

paper: P1901

lib: true

support: [GCC 16, Clang 24]

ftm:

- name: __cpp_lib_smart_ptr_owner_equality

value: 202306L

- desc: "`std::text_encoding`: text encodings identification"

paper: [P1885, P2862]

lib: true

support: [GCC 14, Clang 23]

ftm:

- name: __cpp_lib_text_encoding

value: 202306L

- desc: "`std::function_ref`: type-erased callable reference"

paper: P0792

summary: "A lightweight, non-owning reference to a callable."

lib: true

support: [GCC 16, Clang 24]

ftm:

- name: __cpp_lib_function_ref

value: 202306L

- desc: "Type-checking format args"

paper: P2757

lib: true

support: [GCC 15]

ftm:

- name: __cpp_lib_format

value: 202305L

- desc: "Member `visit` (`std::variant::visit()`)"

paper: P2637

summary: "`std::variant` now has a member `.visit()` function."

lib: true

support:

- GCC 15

- Clang 19

- Xcode 16.3

ftm:

- name: __cpp_lib_variant

value: 202306L

- name: __cpp_lib_format

value: 202306L

- desc: "Checking if a union alternative is active (`std::is_within_lifetime()`)"

paper: P2641

lib: true

ftm:

- name: __cpp_lib_is_within_lifetime

value: 202306L

support: [Clang 22]

- desc: "Native handles and file streams"

paper: P1759

lib: true

support:

- GCC 14

- Clang 18

- Xcode 16

ftm:

- name: __cpp_lib_fstream_native_handle

value: 202306L

- desc: "Interfacing `std::bitset` with `std::string_view`"

paper: P2697

lib: true

support:

- Clang 18

- Xcode 16

- GCC 16

ftm:

- name: __cpp_lib_bitset

value: 202306L

- desc: "More constexpr for `<cmath>` and `<complex>`"

paper: P1383

summary: "More mathematical functions are now `constexpr`, such as `std::sqrt`."

content: more-constexpr-cmath.md

lib: true

support: [GCC 4.6 (partial)]

ftm:

- name: __cpp_lib_constexpr_cmath

value: 202306L

- name: __cpp_lib_constexpr_complex

value: 202306L

- desc: "Adding the new 2022 SI prefixes (`std::quecto`, `std::ronto`, `std::ronna`, `std::quetta`)"

paper: P2734

lib: true

support:

- GCC 14

- tool: Clang 17

status: partial

note: "Only the feature-testing macro has been added (`__cpp_lib_ratio`)."

ftm:

- name: __cpp_lib_ratio

value: 202306L

- desc: "`std::copyable_function`"

paper: P2548

summary: "A `std::function` variant that guarantees copyability and const-correctness."

content: copyable-function.md

lib: true

ftm:

- name: __cpp_lib_copyable_function

value: 202306L

support: [GCC 16]

- desc: "Bind front and back to NTTP callables (`std::bind_front()`, `std::bind_back()`, `std::not_fn`)"

paper: P2714

lib: true

support: [GCC 16, Clang 20 (partial)]

ftm:

- name: __cpp_lib_bind_front

value: 202306L

desc: "`std::bind_front()` is available"

- name: __cpp_lib_bind_back

value: 202306L

desc: "`std::bind_back()` is available"

- name: __cpp_lib_not_fn

value: 202306L

desc: "`std::not_fn` is available"

- desc: "`std::submdspan()`"

paper: [P2630, P3355]

summary: "Extract sub-views from multidimensional spans."

content: submdspan.md

lib: true

support: [GCC 16]

ftm:

- name: __cpp_lib_submdspan

value: 202306L

- desc: "Template parameter initialization"

paper: P2308

content: template-parameter-init.md

support:

- GCC 9

- Clang 18

- Xcode 16.3

- R++

- desc: "[Pack indexing](https://cppreference.com/cpp/language/pack_indexing)"

paper: P2662

summary: "Pack indexing provides direct access to elements in a parameter pack using `...[N]` syntax."

content: pack-indexing.md

support:

- GCC 15

- Clang 19

- Xcode 16.3

- R++ 2025.3

ftm:

- name: __cpp_pack_indexing

value: 202311L

- desc: "Remove deprecated arithmetic conversion on enumerations"

paper: P2864

support:

- GCC 14

- Clang 18

- Xcode 16.3

- tool: R++

status: unsupported

issue: RSCPP-37865

- desc: "Saturation arithmetic"

paper: [P0543, P4052]

summary: "Arithmetic operations that clamp to min/max instead of overflowing."

content: saturation-arithmetic.md

lib: true

support:

- GCC 14

- Clang 18

- Xcode 16

ftm:

- name: __cpp_lib_saturation_arithmetic

value: 202311L

desc: "`std::add_sat()`, ..., `std::saturate_cast()`"

- name: __cpp_lib_saturation_arithmetic

value: 202603L

desc: "Rename to `std::saturating_add()`, ..., `std::saturating_cast()`"

keywords: ["math"]

- desc: "Freestanding library: Partial Classes"

paper: P2407

lib: true

support: [GCC 14, MSVC 14.42]

ftm:

- name: __cpp_lib_freestanding_algorithm

value: 202311L

- name: __cpp_lib_freestanding_array

value: 202311L

- name: __cpp_lib_freestanding_optional

value: 202311L

- name: __cpp_lib_freestanding_string_view

value: 202311L

- name: __cpp_lib_freestanding_variant

value: 202311L

- desc: "Debugging support (`<debugging>`)"

paper: [P2546, P2810]

summary: "The `<debugging>` header provides portable debugging utilities."

lib: true

support:

- tool: GCC 16

note: "Requires linking with `-lstdc++exp`."

ftm:

- name: __cpp_lib_debugging

value: 202311L

keywords: ["debugger", "breakpoint"]

content: debugging.md

- desc: "Runtime format strings (`std::format()`)"

paper: P2905

content: make-format-args-lvalue.md

lib: true

support:

- GCC 14

- Clang 18

- MSVC 14.40

- Xcode 16

ftm:

- name: __cpp_lib_format

value: 202311L

- desc: "Runtime format strings II (`std::format()`)"

paper: P2918

content: runtime-format.md

lib: true

support:

- GCC 14

- Clang 18

- Xcode 16

ftm:

- name: __cpp_lib_format

value: 202311L

- desc: "Fix formatting of code units as integers (_Dude, where's my char?_)"

paper: P2909

lib: true

support:

- GCC 13.3

- Clang 18

- MSVC 14.40

- Xcode 16

ftm:

- name: __cpp_lib_format_uchar

value: 202311L

- desc: "A new specification for `std::generate_canonical()`"

paper: P0952

lib: true

support: [GCC 16, MSVC 14.42]

- desc: "`std::span::at()`"

paper: P2821

content: span-at.md

lib: true

support:

- GCC 14

- Clang 18

- Xcode 16

ftm:

- name: __cpp_lib_span

value: 202311L

- desc: "Remove deprecated `std::allocator` typedef from C++26 (`std::allocator::is_always_equal()`)"

paper: P2868

lib: true

support:

- GCC 15

- Clang 18

- Xcode 16

- desc: "Remove `std::basic_string::reserve()` from C++26"

paper: P2870

summary: "The overload of `std::basic_string::reserve()` with no parameters is removed. It used to be a poor substitute for `std::basic_string::shrink_to_fit()`."

lib: true

support: [Clang 18, Xcode 16]

- desc: "Remove deprecated Unicode conversion facets from C++26 (`<codecvt>`)"

paper: P2871

lib: true

support: [Clang 18, Xcode 16]

- desc: "Add tuple protocol to complex"

paper: P2819

content: complex-tuple-protocol.md

lib: true

support:

- GCC 15

- Clang 19

- Xcode 16.3

ftm:

- name: __cpp_lib_tuple_like

value: 202311L

- desc: "Freestanding: Remove `strtok()`"

paper: P2937

lib: true

support: [GCC 14, MSVC 14.40]

ftm:

- name: __cpp_lib_freestanding_cstring

value: 202311L

- desc: "Freestanding library: `std::inout`, `std::expected`, `std::span`"

paper: P2833

lib: true

support: [GCC 14, MSVC 14.42]

ftm:

- name: __cpp_lib_freestanding_expected

value: 202311L

- name: __cpp_lib_freestanding_mdspan

value: 202311L

- name: __cpp_lib_out_ptr

value: 202311L

- name: __cpp_lib_span

value: 202311L

desc: 'Related: <a href="https://wg21.link/P2821">P2821</a>'

- desc: "`std::basic_const_iterator` should follow its underlying type's convertibility"

paper: [P2836, P2950]

lib: true

support: [GCC 14, MSVC 14.40]

ftm:

- name: __cpp_lib_ranges_as_const

value: 202311L

- desc: "Make `assert()` macro user friendly for C and C++"

paper: P2264

content: assert-variadic.md

lib: true

- desc: "A free function linear algebra interface based on the BLAS (`<linalg>`)"

paper: [P1673, P3050, P3222]

lib: true

ftm:

- name: __cpp_lib_linalg

value: 202311L

keywords: ["math"]

- desc: "Disallow binding a returned [glvalue](https://cppreference.com/cpp/language/value_category#glvalue) to a temporary"

paper: P2748

content: disallow-return-temporary-glvalue.md

support:

- GCC 14

- Clang 19

- Xcode 16.3

- tool: R++

status: unsupported

- desc: "Clarifying rules for brace elision in [aggregate initialization](https://cppreference.com/cpp/language/aggregate_initialization)"

paper: P3106

support:

- GCC

- Clang 17

- Xcode 16.3

- R++

- desc: "Attributes for [structured bindings](https://cppreference.com/cpp/language/structured_binding)"

paper: P0609

support:

- GCC 15

- Clang 19

- Xcode 16.3

- R++ 2025.2

ftm:

- name: __cpp_structured_bindings

value: 202403L

- desc: "Module declarations shouldn't be macros"

paper: P3034

support: [GCC 15, Clang 23]

- desc: "Trivial infinite loops are not undefined behavior"

paper: P2809

support:

- GCC 14

- Clang 19

- Xcode 16.3

- R++

content: trivial-infinite-loops.md

keywords: ["safety"]

- desc: "Erroneous behavior for uninitialized reads (and `[[indeterminate]]` attribute)"

paper: P2795

support: [GCC 16]

keywords: ["safety"]

- desc: '= delete("should have a reason");'

paper: P2573

summary: "Deleted functions can now include a message explaining why they're deleted."

content: delete-reason.md

support:

- GCC 15

- Clang 19

- Xcode 16.3

- R++ 2025.2

ftm:

- name: __cpp_deleted_function

value: 202403L

- desc: "Variadic friends"

paper: P2893

summary: "Class templates can now declare all types in a parameter pack as friends."

support: [GCC 15, Clang 20, Xcode 26.4, R++ 2025.2]

ftm:

- name: __cpp_variadic_friend

value: 202403L

- desc: "Undeprecate `std::polymorphic_allocator::destroy()` for C++26"

paper: P2875

lib: true

support: [GCC 14.3, Clang 15, MSVC 14.41]

- desc: "Remove deprecated strstreams from C++26"

paper: P2867

lib: true

support: [Clang 19]

keywords: ["safety"]

- desc: "Remove deprecated `std::shared_ptr` atomic access APIs from C++26"

paper: P2869

lib: true

- desc: "Remove `std::wstring_convert` from C++26"

paper: P2872

lib: true

support: [Clang 19]

- desc: "Permit an efficient implementation of `std::print()`"

paper: [P3107, P3235]

lib: true

support: [GCC 16, MSVC 14.43]

ftm:

- name: __cpp_lib_print

value: 202403L

keywords: ["format"]

- desc: "Printing blank lines with `std::println()`"

paper: P3142

lib: true

content: println-blank-lines.md

support:

- GCC 14

- Clang 19

- MSVC 14.41

- Xcode 16.3

ftm:

- name: __cpp_lib_print

value: 202403L

keywords: ["format"]

- desc: "Formatting of `filesystem::path` (`std::formatter<filesystem::path>`)"

paper: P2845

lib: true

support: [GCC 16]

ftm:

- name: __cpp_lib_format_path

value: 202403L

- desc: "`views::concat()`"

paper: P2542

lib: true

support: [GCC 15, Clang 23]

ftm:

- name: __cpp_lib_ranges_concat

value: 202403L

- desc: "Concatenation of `std::string` and `std::string_view`"

paper: P2591

lib: true

support:

- GCC 15

- Clang 19

- Xcode 16.3

ftm:

- name: __cpp_lib_string_view

value: 202403L

- desc: "Enabling list-initialization for algorithms"

paper: [P2248, P3217]

lib: true

support: [GCC 15]

ftm:

- name: __cpp_lib_algorithm_default_value_type

value: 202403L

- desc: "Vector API for random number generation (`ranges::generate_random()`)"

paper: P1068

lib: true

ftm:

- name: __cpp_lib_ranges_generate_random

value: 202403L

- desc: "Comparisons for `std::reference_wrapper` (and constraints for comparisons of `std::pair`, `std::tuple`, `std::optional`, and `std::variant`)"

paper: P2944

lib: true

support:

- GCC 14

- tool: Clang 19

status: partial

note: "Constrained equality is not implemented."

- tool: Clang 22

note: "The changes to `tuple`'s equality overload from P2165 are not yet implemented."

ftm:

- name: __cpp_lib_constrained_equality

value: 202403L

desc: "Constrained relational operators for `std::pair`, `std::tuple`, `std::optional` and `std::variant`"

- name: __cpp_lib_reference_wrapper

value: 202403L

desc: "Comparisons for `std::reference_wrapper`"

- desc: "Padded `std::mdspan` layouts"

paper: P2642

lib: true

support: [GCC 16]

ftm:

- name: __cpp_lib_submdspan

value: 202403L

- desc: "Better `std::mdspan`'s [CTAD](https://cppreference.com/cpp/language/class_template_argument_deduction)"

paper: P3029

lib: true

support: [GCC 16, Clang 19]

- desc: "`constexpr` placement `new`"

paper: P2747

summary: "Placement `new` can now be used in constant expressions."

support:

- GCC 15

- Clang 20

- Xcode 26.4

- R++ 2025.3

ftm:

- name: __cpp_constexpr

value: 202406L

- name: __cpp_lib_constexpr_new

value: 202406L

- desc: "Deleting a pointer to an incomplete type should be ill-formed"

paper: P3144

support:

- GCC 15

- Clang 19

- Xcode 16.3

- R++

- desc: "Ordering of constraints involving fold expressions"

paper: P2963

support:

- Clang 19

- Xcode 16.3

- tool: R++

status: unsupported

ftm:

- name: __cpp_fold_expressions

value: 202406L

- desc: "Structured binding declaration as a condition"

paper: P0963

summary: "Structured bindings can now be used directly in `if` and `while` conditions."

support:

- GCC 15

- tool: Clang 6

status: partial

note: "Supported as an extension, not fully conforming to standardized version."

- Clang 21

- Xcode 26.4

- R++

ftm:

- name: __cpp_structured_bindings

value: 202406L

keywords: [decompose]

- desc: "Removing the common reference requirement from the indirectly invocable concepts"

paper: P2997

lib: true

support:

- GCC 15

- Clang 19

- MSVC 14.42

- desc: "dextents index type parameter (`std::dims`)"

paper: P2389

lib: true

support: [GCC 16, Clang 19]

ftm:

- name: __cpp_lib_mdspan

value: 202406L

- desc: "Give `std::optional` range support"

paper: P3168

summary: "`std::optional` is now a range containing zero or one elements."

lib: true

support: [GCC 16, Clang 22]

ftm:

- name: __cpp_lib_optional_range_support

value: 202406L

- desc: "A type trait for detecting virtual base classes (`std::is_virtual_base_of`)"

paper: P2985

lib: true

support:

- GCC 15

- Clang 20

- Xcode 26

ftm:

- name: __cpp_lib_is_virtual_base_of

value: 202406L

- desc: "`std::inplace_vector`: dynamically-resizable vector with fixed capacity (`<inplace_vector>`)"

paper: P0843

summary: "A fixed-capacity vector that stores elements inline without heap allocation."

content: inplace-vector.md

lib: true

support: [GCC 16]

ftm:

- name: __cpp_lib_inplace_vector

value: 202406L

- desc: "Make `std::ignore` a first-class object"

paper: P2968

lib: true

support:

- GCC 15

- Clang 19

- MSVC 14.42

- desc: "Philox as an extension of the C++ RNG engines (`std::philox_engine`)"

paper: P2075

lib: true

ftm:

- name: __cpp_lib_philox_engine

value: 202406L

support: [GCC 16]

keywords: ["random"]

- desc: "`std::execution` (`<execution>`)"

paper: [P2300, P3396]

summary: "A framework for asynchronous and parallel programming based on senders and receivers."

lib: true

ftm:

- name: __cpp_lib_senders

value: 202406L

content: execution.md

- desc: "`constexpr` structured bindings and references to `constexpr` variables"

paper: P2686

support:

- tool: GCC 16

status: partial

note: "No [references to constexpr variables](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117784)."

- tool: Clang 22

status: partial

note: "References to `constexpr` and decomposition of tuple-like types are not supported (only arrays and aggregates are)."

- R++

- desc: "Allowing exception throwing in constant-evaluation (`constexpr` exceptions)"

paper: P3068

summary: "Exceptions can now be thrown and caught during constant evaluation."

content: constexpr-exceptions.md

support: [GCC 16, R++ 2026.2]

ftm:

- name: __cpp_constexpr_exceptions

value: 202411L

- desc: "Deprecate the notion of trivial types (`std::is_trivial` and `std::is_trivial_v`)"

paper: P3247

lib: true

support: [GCC 15, Clang 21, Xcode 26.4]

- desc: "Remove deprecated array comparisons from C++26"

paper: P2865

support:

- GCC 15

- Clang 20

- Xcode 16

- tool: R++

status: unsupported

keywords: ["safety"]

- desc: "[Structured bindings](https://cppreference.com/cpp/language/structured_binding) can introduce a pack"

paper: P1061

summary: "Structured bindings can now capture remaining elements into a parameter pack."

support: [GCC 16, Clang 21, Xcode 26.4, R++ 2025.3]

ftm:

- name: __cpp_structured_bindings

value: 202411L

- desc: "The Oxford variadic comma"

paper: P3176

support:

- GCC 15

- Clang 20

- Xcode 26.4

- tool: R++

status: unsupported

summary: "Variadic ellipsis parameters (`...`) without a separating comma are deprecated, such as `int...`."

content: oxford-variadic-comma.md

- desc: "Retiring niebloids"

paper: P3136

lib: true

support:

- GCC

- Clang 14

- MSVC 14.39

- Xcode 14.3

- desc: "`views::cache_latest()` (`views::cache_latest_view`)"

paper: P3138

summary: "Cache the most recent element for repeated access."

lib: true

support: [GCC 15]

ftm:

- name: __cpp_lib_ranges_cache_latest

value: 202411L

- desc: "Constrain `std::expected` equality operators"

paper: P3379

lib: true

support: [GCC 15, Clang 21]

ftm:

- name: __cpp_lib_constrained_equality

value: 202411L

- desc: "`std::aligned_accessor`: An `std::mdspan` accessor expressing pointer over-alignment (and `std::is_sufficiently_aligned()`)"

paper: P2897

lib: true

support: [GCC 16, Clang 21, Xcode 26.4]

ftm:

- name: __cpp_lib_aligned_accessor

value: 202411L

- desc: "Expose `std::atomic_ref`'s object address (`std::atomic_ref::address()`)"

paper: [P2835, P3936]

lib: true

support:

- tool: Clang 22

status: partial

note: "Supports the older proposal, with a different return type."

- Clang 23

- GCC 16

ftm:

- name: __cpp_lib_atomic_ref

value: 202411L

- name: __cpp_lib_atomic_ref

value: 202603L

- desc: "cv-qualified types in `std::atomic` and `std::atomic_ref`"

paper: P3323

lib: true

support: [GCC 16, MSVC 14.44]

- desc: 'Wording for "`constexpr` for specialized memory algorithms"'

paper: P3508