features_cpp26.yaml

---
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://en.cppreference.com/w/cpp/language/string_literal.html#Unevaluated_strings)"
    paper: P2361
    support:
      - GCC 14
      - Clang 17 (partial)
      - Clang 18
      - Xcode 16
    hints:
      - target: Clang 17
        msg: "Attributes arguments don't yet parse as unevaluated string literals."

  - desc: "Add @, $, and ` to the [basic character set](https://en.cppreference.com/w/cpp/language/charset.html#Basic_character_set)"
    paper: P2558
    support:
      - GCC 15
      - Clang
      - Xcode 15

  - desc: "`constexpr` cast from `void*`: towards `constexpr` type-erasure"
    paper: P2738
    support:
      - GCC 14
      - Clang 17
      - Xcode 16.3
    ftm:
      - name: __cpp_constexpr
        value: 202306L

  - 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]

  - 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
    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
    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]
    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
    ftm:
      - name: __cpp_lib_atomic_min_max
        value: 202403L

  - desc: "Extending associative containers with the remaining heterogeneous overloads"
    paper: P2363
    lib: true
    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]
    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]
    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]
    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
    lib: true
    support: [GCC 4.6]
    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, Clang 17 (partial)]
    ftm:
      - name: __cpp_lib_ratio
        value: 202306L
    hints:
      - target: Clang 17
        msg: "Only the feature-testing macro has been added (`__cpp_lib_ratio`)."

  - 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

  - desc: "[Pack indexing](https://en.cppreference.com/w/cpp/language/pack_indexing.html)"
    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
    ftm:
      - name: __cpp_pack_indexing
        value: 202311L

  - desc: "Remove deprecated arithmetic conversion on enumerations"
    paper: P2864
    support:
      - GCC 14
      - Clang 18
      - Xcode 16.3

  - desc: "Saturation arithmetic"
    paper: P0543
    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
    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: [GCC 16 (hint)]
    hints:
      - target: GCC 16
        msg: "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` over an initializer list"
    paper: P2447
    content: span-initializer-list.md
    lib: true
    support:
      - GCC 15
      - Clang 18
      - Xcode 16
    ftm:
      - name: __cpp_lib_span_initializer_list
        value: 202311L

  - 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
    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://en.cppreference.com/w/cpp/language/value_category.html#glvalue) to a temporary"
    paper: P2748
    support:
      - GCC 14
      - Clang 19
      - Xcode 16.3

  - desc: "Clarifying rules for brace elision in [aggregate initialization](https://en.cppreference.com/w/cpp/language/aggregate_initialization.html)"
    paper: P3106
    support:
      - GCC
      - Clang 17
      - Xcode 16.3

  - desc: "Attributes for [structured bindings](https://en.cppreference.com/w/cpp/language/structured_binding.html)"
    paper: P0609
    support:
      - GCC 15
      - Clang 19
      - Xcode 16.3
    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
    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
    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]
    ftm:
      - name: __cpp_variadic_friend
        value: 202403L

  - desc: "Undeprecate `std::polymorphic_allocator::destroy()` for C++26"
    paper: P2875
    lib: true
    support: [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
    ftm:
      - name: __cpp_lib_format_path
        value: 202403L

  - desc: "`views::concat()`"
    paper: P2542
    lib: true
    support: [GCC 15]
    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
      - Clang 19 (partial)
      - Clang 22 (hint)
    hints:
      - target: Clang 19
        msg: "Constrained equality is not implemented."
      - target: Clang 22
        msg: "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://en.cppreference.com/w/cpp/language/class_template_argument_deduction.html)"
    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
    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

  - desc: "Ordering of constraints involving fold expressions"
    paper: P2963
    support: [Clang 19, Xcode 16.3]
    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
      - Clang 6 (partial)
      - Clang 21
    hints:
      - target: Clang 6
        msg: "Supported as an extension, not fully conforming to standardized version."
    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: [GCC 16 (partial), Clang 22 (partial)]
    hints:
      - target: GCC 16
        msg: "No [references to constexpr variables](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117784)."
      - target: Clang 22
        msg: "References to `constexpr` and decomposition of tuple-like types are not supported (only arrays and aggregates are)."

  - 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]
    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]

  - desc: "Remove deprecated array comparisons from C++26"
    paper: P2865
    support:
      - GCC 15
      - Clang 20
      - Xcode 16
    keywords: ["safety"]

  - desc: "[Structured bindings](https://en.cppreference.com/w/cpp/language/structured_binding.html) can introduce a pack"
    paper: P1061
    summary: "Structured bindings can now capture remaining elements into a parameter pack."
    support: [GCC 16, Clang 21]
    ftm:
      - name: __cpp_structured_bindings
        value: 202411L

  - desc: "The Oxford variadic comma"
    paper: P3176
    support: [GCC 15, Clang 20]

  - 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]
    ftm:
      - name: __cpp_lib_aligned_accessor
        value: 202411L

  - desc: "Expose `std::atomic_ref`'s object address (`std::atomic_ref::address()`)"
    paper: P2835
    lib: true
    support: [Clang 22]
    ftm:
      - name: __cpp_lib_atomic_ref
        value: 202411L

  - 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
    lib: true
    support: [GCC 15]
    ftm:
      - name: __cpp_lib_raw_memory_algorithms
        value: 202411L

  - desc: "`constexpr` for `std::uninitialized_default_construct()`"
    paper: P3369
    lib: true
    ftm:
      - name: __cpp_lib_raw_memory_algorithms
        value: 202411L

  - desc: "Add new library headers from C23 (`<stdbit.h>` and `<stdckdint.h>`)"
    paper: P3370
    lib: true
    support: [GCC 15]

  - desc: "`constexpr` `std::atomic` and `std::atomic_ref`"
    paper: P3309
    lib: true
    ftm:
      - name: __cpp_lib_constexpr_atomic
        value: 202411L

  - desc: "`std::simd` (`<simd>`)"
    paper: [P1928, P3430, P3287]
    summary: "Portable SIMD (Single Instruction, Multiple Data) vector types."
    content: simd.md
    lib: true
    ftm:
      - name: __cpp_lib_simd
        value: 202411L
      - name: __cpp_lib_simd_complex
        value: 202502L
        desc: "Support for interleaved complex values in std::datapar::simd"

  - desc: "Utility for creating execution environments"
    paper: P3325
    lib: true

  - desc: "Trivial unions (was `std::uninitialized<T>`)"
    paper: P3074
    content: trivial-unions.md
    ftm:
      - name: __cpp_trivial_union
        value: 202502L

  - desc: "`constexpr` `std::inplace_vector` for non-trivial types"
    paper: P3074
    lib: true
    ftm:
      - name: __cpp_lib_constexpr_inplace_vector
        value: 202502L

  - desc: "Partial program correctness (`std::observable()`)"
    paper: P1494
    support: [GCC 16]
    keywords: ["safety"]

  - desc: "Contracts for C++ (`<contracts>`)"
    paper: P2900
    summary: "Contracts let you specify preconditions, postconditions, and assertions that document and enforce function requirements."
    ftm:
      - name: __cpp_contracts
        value: 202502L
        desc: "Core language feature"
      - name: __cpp_lib_contracts
        value: 202502L
        desc: "Library API is available. This is a separate macro to allow for mixing language (compiler) support with different standard library implementations, where this macro specifies the level of support for contracts by that standard library implementation."
    keywords: ["safety"]
    content: contracts.md

  - desc: "Defang and deprecate `std::memory_order::consume`"
    paper: P3475
    lib: true

  - desc: "Concept and variable-template template-parameters"
    paper: P2841
    ftm:
      - name: __cpp_template_parameters
        value: 202502L

  - desc: "`#embed` - a scannable, tooling-friendly binary resource inclusion mechanism"
    paper: P1967
    summary: "`#embed` allows you to include binary files directly into your source code at compile time."
    support:
      - GCC 15 (hint)
      - Clang 19 (hint)
      - Xcode 16.3 (hint)
    hints:
      - target: GCC 15
        msg: >
          Although this is a C++26 feature, this is available in GCC starting with C++20 (`-std=c++20`).

      - target: Clang 19
        msg: >
          Supported as an extension.<br>
          Use the flag `-Wno-c23-extensions` to suppress warnings related to `#embed`.<br>
          Although this is a C++26 feature, this is available in Clang starting with C++20 (`-std=c++20`).<br>
          Clang does not define the `__cpp_pp_embed` feature-testing macro yet.

      - target: Xcode 16.3
        msg: >
          Supported as an extension.<br>
          Use the flag `-Wno-c23-extensions` to suppress warnings related to `#embed`.<br>
          Although this is a C++26 feature, this is available in Apple Clang starting with C++20 (`-std=c++20`).<br>
          Apple Clang does not define the `__cpp_pp_embed` feature-testing macro yet.
    ftm:
      - name: __cpp_pp_embed
        value: 202502L
    content: embed.md

  - desc: "`views::to_input()` (`ranges::to_input_view`)"
    paper: P3137
    summary: "Convert any range to an input range."
    lib: true
    support: [GCC 15]
    ftm:
      - name: __cpp_lib_ranges_to_input
        value: 202502L

  - desc: "Put `std::monostate` in `<utility>`"
    paper: P0472
    lib: true
    support:
      - GCC 15
      - Clang 21
      - MSVC 14.50

  - desc: "Converting contiguous iterators to pointers"
    paper: P3349
    lib: true
    support: [GCC 15, MSVC 14.51]

  - desc: "`constexpr` containers and adaptors"
    paper: P3372
    summary: "More standard containers work at compile time."
    content: constexpr-containers.md
    lib: true
    ftm:
      - name: __cpp_lib_constexpr_deque
        value: 202502L
        desc: "`constexpr` `std::deque`"
      - name: __cpp_lib_constexpr_flat_map
        value: 202502L
        desc: "`constexpr` `std::flat_map`"
      - name: __cpp_lib_constexpr_flat_set
        value: 202502L
        desc: "`constexpr` `std::flat_set`"
      - name: __cpp_lib_constexpr_forward_list
        value: 202502L
        desc: "`constexpr` `std::forward_list`"
      - name: __cpp_lib_constexpr_list
        value: 202502L
        desc: "`constexpr` `std::list`"
      - name: __cpp_lib_constexpr_map
        value: 202502L
        desc: "`constexpr` `std::map`"
      - name: __cpp_lib_constexpr_queue
        value: 202502L
        desc: "`constexpr` `std::queue`"
      - name: __cpp_lib_constexpr_set
        value: 202502L
        desc: "`constexpr` `std::set`"
      - name: __cpp_lib_constexpr_stack
        value: 202502L
        desc: "`constexpr` `std::stack`"
      - name: __cpp_lib_constexpr_unordered_map
        value: 202502L
        desc: "`constexpr` `std::unordered_map`"
      - name: __cpp_lib_constexpr_unordered_set
        value: 202502L
        desc: "`constexpr` `std::unordered_set`"

  - desc: "`constexpr` exception types"
    paper: P3378
    content: constexpr-exception-types.md
    lib: true
    ftm:
      - name: __cpp_lib_constexpr_exceptions
        value: 202411L
    support: [GCC 16]

  - desc: "Rename `simd_split()` to `simd_chunk()`"
    paper: P3441
    lib: true

  - desc: "Freestanding library: `<algorithm>`, `<numeric>`, and `<random>`"
    paper: P2976
    lib: true
    ftm:
      - name: __cpp_lib_freestanding_algorithm
        value: 202502L
      - name: __cpp_lib_freestanding_execution
        value: 202502L
      - name: __cpp_lib_freestanding_memory
        value: 202502L
      - name: __cpp_lib_freestanding_numeric
        value: 202502L
      - name: __cpp_lib_freestanding_random
        value: 202502L

  - desc: "Interleaved complex values support in `std::simd`"
    paper: P2663
    lib: true
    ftm:
      - name: __cpp_lib_simd_complex
        value: 202502L

  - desc: "Extend `<bit>` header function with overloads for `std::simd`"
    paper: P2933
    lib: true
    ftm:
      - name: __cpp_lib_simd
        value: 202506L

  - desc: "`ranges::approximately_sized_range` and `ranges::reserve_hint()`"
    paper: P2846
    summary: "Ranges can provide size hints for better allocation."
    lib: true
    ftm:
      - name: __cpp_lib_ranges_reserve_hint
        value: 202502L

  - desc: "Standard library hardening"
    paper: P3471
    lib: true
    support:
      - GCC 15 (partial)
      - Clang 18 (partial)
      - MSVC 14.44 (partial)
      - Xcode 16 (partial)
    hints:
      - target: GCC 15
        msg: "Calls `abort()` instead of using C++26 contracts when a hardened precondition is violated."
      - target: Clang 18
        msg: "Calls `__builtin_expect(false, ...)` instead of using C++26 contracts when a hardened precondition is violated."
      - target: MSVC 14.44
        msg: "Calls `__fastfail()` instead of using C++26 contracts when a hardened precondition is violated."
      - target: Xcode 16
        msg: "Calls `__builtin_expect(false, ...)` instead of using C++26 contracts when a hardened precondition is violated."
    ftm:
      - name: __cpp_lib_hardened_array
        desc: "Hardened `std::array`"
        value: 202502L
      - name: __cpp_lib_hardened_basic_string
        desc: "Hardened `std::basic_string`"
        value: 202502L
      - name: __cpp_lib_hardened_basic_string_view
        desc: "Hardened `std::basic_string_view`"
        value: 202502L
      - name: __cpp_lib_hardened_bitset
        desc: "Hardened `std::bitset`"
        value: 202502L
      - name: __cpp_lib_hardened_deque
        desc: "Hardened `std::deque`"
        value: 202502L
      - name: __cpp_lib_hardened_expected
        desc: "Hardened `std::expected`"
        value: 202502L
      - name: __cpp_lib_hardened_forward_list
        desc: "Hardened `std::forward_list`"
        value: 202502L
      - name: __cpp_lib_hardened_inplace_vector
        desc: "Hardened `std::inplace_vector`"
        value: 202502L
      - name: __cpp_lib_hardened_list
        desc: "Hardened `std::list`"
        value: 202502L
      - name: __cpp_lib_hardened_mdspan
        desc: "Hardened `std::mdspan`"
        value: 202502L
      - name: __cpp_lib_hardened_optional
        desc: "Hardened `std::optional`"
        value: 202502L
      - name: __cpp_lib_hardened_span
        desc: "Hardened `std::span`"
        value: 202502L
      - name: __cpp_lib_hardened_valarray
        desc: "Hardened `std::valarray`"
        value: 202502L
      - name: __cpp_lib_hardened_vector
        desc: "Hardened `std::vector`"
        value: 202502L
    keywords: ["safety"]
    content: hardening.md

  - desc: "`std::hive` (`<hive>`)"
    paper: P0447
    summary: "A container optimized for frequent insert/erase with stable iterators."
    content: hive.md
    lib: true
    ftm:
      - name: __cpp_lib_hive
        value: 202502L
    keywords: ["container"]

  - desc: "`std::indirect` and `std::polymorphic`: Vocabulary Types for Composite Class Design"
    paper: P3019
    summary: "Value-semantic wrappers for indirect and polymorphic ownership."
    lib: true
    support: [GCC 16]
    ftm:
      - name: __cpp_lib_indirect
        value: 202502L
        desc: "`std::indirect` is available"
      - name: __cpp_lib_polymorphic
        value: 202502L
        desc: "`std::polymorphic` is available"

  - desc: "Allow attaching `main()` to the global module"
    paper: P3618
    support: [GCC 16, Clang 21]

  - desc: "Reflection for C++26 (`<meta>`)"
    paper: P2996
    summary: "Reflection allows programs to inspect and manipulate their own structure at compile time. This is one of the most significant additions to C++26."
    lib: true
    support: [GCC 16 (hint)]
    hints:
      - target: GCC 16
        msg: "Requires `-freflection`"
    ftm:
      - name: __cpp_impl_reflection
        value: 202506L
    content: reflection.md

  - desc: "Annotations for Reflection"
    paper: P3394
    support: [GCC 16]

  - desc: "Splicing a base class subobject"
    paper: P3293
    support: [GCC 16]
    keywords: ["reflection"]

  - desc: "`define_static_{string,object,array}`"
    paper: P3491
    lib: true
    support: [GCC 16]
    ftm:
      - name: __cpp_lib_define_static
        value: 202506L
    keywords: ["reflection"]

  - desc: "Expansion Statements (`template for`)"
    paper: P1306
    summary: "`template for` iterates over compile-time ranges like tuples and reflection results."
    content: expansion-statements.md
    support: [GCC 16]
    ftm:
      - name: __cpp_expansion_statements
        value: 202506L
    keywords: ["reflection"]

  - desc: "Function Parameter Reflection in Reflection for C++26"
    paper: P3096
    lib: true
    support: [GCC 16]

  - desc: "`constexpr` virtual inheritance"
    paper: P3533
    content: constexpr-virtual-inheritance.md
    support: [GCC 16]
    ftm:
      - name: __cpp_constexpr_virtual_inheritance
        value: 202506L

  - desc: "Preprocessing is never undefined"
    paper: P2843
    support: [GCC 16]

  - desc: "`std::optional<T&>`"
    paper: P2988
    summary: "`std::optional` can now hold references, not just values."
    lib: true
    support: [GCC 16, Clang 22]
    ftm:
      - name: __cpp_lib_freestanding_optional
        value: 202506L
      - name: __cpp_lib_optional
        value: 202506L
    content: optional-ref.md

  - desc: "`constexpr` `std::shared_ptr` and friends"
    paper: P3037
    lib: true
    ftm:
      - name: __cpp_lib_constexpr_memory
        value: 202506L

  - desc: "`execution::write_env` and unstoppable sender adaptors"
    paper: P3284
    lib: true

  - desc: "Parallel range algorithms"
    paper: P3179
    summary: "Range algorithms now support parallel execution policies."
    lib: true
    ftm:
      - name: __cpp_lib_parallel_algorithm
        value: 202506L

  - desc: "Reconsider parallel `ranges::rotate_copy()` and `ranges::reverse_copy()`"
    paper: P3709
    lib: true

  - desc: "Rename `std::observable()` to `std::observable_checkpoint()`, and add a feature-test macro"
    paper: P3641
    lib: true

  - desc: "`std::string::subview()`"
    paper: P3044
    lib: true
    ftm:
      - name: __cpp_lib_string_subview
        value: 202506L
    support: [GCC 16, Clang 22]

  - desc: "Proposal to extend `std::simd` with more constructors and accessors"
    paper: P2876
    lib: true

  - desc: "`std::simd` is a range"
    paper: P3480
    lib: true
    ftm:
      - name: __cpp_lib_simd
        value: 202506L

  - desc: "Extend `std::simd` with permutation API"
    paper: P2664
    lib: true
    ftm:
      - name: __cpp_lib_simd_permutations
        value: 202506L

  - desc: "Reconsider naming of the namespace for `std::simd`"
    paper: P3691
    lib: true

  - desc: "`std::mdspan::at()`"
    paper: P3383
    lib: true

  - desc: "Inspecting `std::exception_ptr`"
    paper: P2927
    summary: "Query exception information without rethrowing."
    lib: true
    support: [GCC 16]

  - desc: "Inspecting `std::exception_ptr` should be `constexpr`"
    paper: P3748
    lib: true
    ftm:
      - name: __cpp_lib_exception_ptr_cast
        value: 202506L
    support: [GCC 16]

  - desc: "Standardized `constexpr` type ordering"
    paper: P2830
    summary: "A standard way to order types at compile time."
    lib: true
    ftm:
      - name: __cpp_lib_type_order
        value: 202506L
    support: [GCC 16]

  - desc: "`std::optional` variants in sender/receiver"
    paper: P3570
    lib: true
    ftm:
      - name: __cpp_lib_senders
        value: 202506L

  - desc: "`std::execution::bulk()` issues"
    paper: P3481
    lib: true

  - desc: "Allocator support for operation states"
    paper: P3433
    lib: true

  - desc: "`async_scope` - Creating scopes for non-sequential concurrency"
    paper: P3149
    lib: true
    ftm:
      - name: __cpp_lib_counting_scope
        value: 202506L

  - desc: "Remove `std::execution::split()`"
    paper: P3682
    lib: true

  - desc: "Parallel scheduler"
    paper: P2079
    lib: true
    ftm:
      - name: __cpp_lib_parallel_scheduler
        value: 202506L

  - desc: "High-quality sender diagnostics with `constexpr` exceptions"
    paper: P3557
    lib: true

  - desc: "Error Handling in Reflection"
    paper: P3560
    lib: true
    support: [GCC 16]
    ftm:
      - name: __cpp_lib_reflection
        value: 202506L

  - desc: "Make type-erased allocator use in `std::promise` and `std::packaged_task` consistent"
    paper: P3503
    lib: true
    support: [MSVC 14.51]

  - desc: "Atomic floating-point min/max"
    paper: P3008
    lib: true
    ftm:
      - name: __cpp_lib_atomic_min_max
        value: 202506L

  - desc: "Atomic reduction operations"
    paper: P3111
    lib: true
    ftm:
      - name: __cpp_lib_atomic_reductions
        value: 202506L

  - desc: "Add `std::views::indices(n)`"
    paper: P3060
    summary: "Generate a range of indices from 0 to n-1."
    lib: true
    support: [GCC 16, Clang 22]
    ftm:
      - name: __cpp_lib_ranges_indices
        value: 202506L

  - desc: "Prevent path presentation problems"
    paper: P2319
    lib: true
    ftm:
      - name: __cpp_lib_format_path
        value: 202506L

  - desc: "Making `std::istream::ignore` less surprising"
    paper: P3223
    lib: true
    support:
      - GCC 16
      - Clang 22
      - MSVC 14.50

  - desc: "`std::constant_wrapper`"
    paper: P2781
    summary: "Wrap compile-time constants as types for template metaprogramming."
    lib: true
    support: [GCC 16]
    ftm:
      - name: __cpp_lib_constant_wrapper
        value: 202506L

  - desc: "Minor additions to C++26 standard library hardening"
    paper: P3697
    content: hardening-additions.md
    lib: true
    support: [MSVC 14.50 (partial)]
    hints:
      - target: MSVC 14.50
        msg: Partial support only due to the lack of Contracts. Support starting with Visual Studio 2026 18.0 Preview 2. ([GitHub Issue](https://github.com/microsoft/STL/pull/5650))
    keywords: ["safety"]

  - desc: "Add a coroutine task type"
    paper: P3552
    summary: "A standard coroutine task type for async operations."
    lib: true
    ftm:
      - name: __cpp_lib_task
        value: 202506L

  - desc: "Remove return type deduction in `std::apply()`"
    paper: P1317
    lib: true
    ftm:
      - name: __cpp_lib_apply
        value: 202506L

  - desc: "Fix erroneous behaviour termination semantics for C++26"
    paper: P3684
    keywords: ["safety"]

  - desc: "Resolve inconsistencies in begin/end for `std::valarray` and braced initializer lists"
    paper: P3016
    lib: true
    support: [MSVC 14.51]

  - desc: "`flat_meow` fixes"
    paper: P3567
    lib: true
    support: [Clang 22, MSVC 14.51]
    ftm:
      - name: __cpp_lib_flat_map
        value: 202511L
        desc: "Fixes for `std::flat_map` and `std::flat_multimap`"
      - name: __cpp_lib_flat_set
        value: 202511L
        desc: "Fixes for `std::flat_set` and `std::flat_multiset`"
    keywords: ["insert_range", "map", "multimap", "set", "multiset"]

  - desc: "Future-proof `submdspan_mapping`"
    paper: P3663
    lib: true

  - desc: "Make `std::optional<T&>` trivially copyable"
    paper: P3836
    lib: true
    support: [Clang 22]

  - desc: "When Do You Know `execution::connect()` Doesn’t Throw?"
    paper: P3388
    lib: true

  - desc: "Rename `std::nontype`, and make it broadly useful"
    paper: P3774
    lib: true

  - desc: "Remove `evaluation_exception()` from contract-violation handling for C++26"
    paper: P3819
    lib: true

  - desc: "Library Support for Expansion Statements"
    paper: P1789
    lib: true
    support: [Clang 22]
    ftm:
      - name: __cpp_lib_integer_sequence
        value: 202511L
    keywords: ["reflection"]

  - desc: "Missing deduction guide from `simd::mask` to `simd::vec`"
    paper: P3922
    lib: true
    ftm:
      - name: __cpp_lib_simd
        value: 202511L

  - desc: "Standard library hardening should not use the 'observe' semantic"
    paper: P3878
    lib: true
    keywords: ["safety"]

  - desc: "Make `execution::when_all()` a Ronseal Algorithm"
    paper: P3887
    lib: true

  - desc: "Fix C++26 by making the rank-1, rank-2, rank-k, and rank-2k updates consistent with the BLAS"
    paper: P3371
    lib: true
    ftm:
      - name: __cpp_lib_linalg
        value: 202511L

  - desc: "`constexpr` `std::format()`"
    paper: P3391
    summary: "`std::format()` can now be used at compile time."
    lib: true
    ftm:
      - name: __cpp_lib_constexpr_format
        value: 202511L

  - desc: "Optimize for `std::optional` in range adaptors"
    paper: P3913
    lib: true