features_cpp20.yaml

---
features:
  - desc: "Default member initializers for bit-fields"
    paper: P0683
    support:
      - GCC 8
      - Clang 6
      - MSVC 14.25
      - Xcode 10
      - R++

  - desc: "`const&`-qualified pointers to members"
    paper: P0704
    support:
      - GCC 8
      - Clang 6
      - MSVC 14.0
      - Xcode 10
      - R++

  - desc: "Allow lambda capture `[=, this]`"
    paper: P0409
    support:
      - GCC 8
      - Clang 6
      - MSVC 14.22
      - Xcode 10
      - R++

  - desc: "`__VA_OPT__`"
    paper: [P0306, P1042]
    summary: "Emit a comma in a variadic macro only when arguments follow."
    support:
      - tool: GCC 8
        status: partial
        note: "`__VA_OPT__` is supported, except `#__VA_OPT__`."
      - tool: GCC 10
        status: partial
        note: "No placemarker token handling changes"
      - GCC 12
      - Clang 9
      - MSVC 14.25
      - Xcode 12
      - R++ 2023.1

  - desc: "Designated initializers"
    paper: P0329
    summary: "Initialize aggregate members by name."
    support:
      - tool: GCC 4.7
        status: partial
        note: "As non-standard extension that formed the basis for P0329, missing brace initializers."
      - GCC 8
      - tool: Clang 3
        status: partial
        note: "Full C99-compatible superset of P0329, missing brace initializers."
      - Clang 10
      - MSVC 14.21
      - Xcode 12
      - R++
    ftm:
      - name: __cpp_designated_initializers
        value: 201707L

  - desc: "Familiar template syntax for generic lambdas (template-able lambdas)"
    paper: P0428
    summary: "Template syntax for lambda parameters."
    support:
      - GCC 8
      - Clang 9
      - MSVC 14.22
      - Xcode 11
      - R++
    ftm:
      - name: __cpp_generic_lambdas
        value: 201707L

  - desc: "Initializer list constructors in class template argument deduction"
    paper: P0702
    support:
      - GCC 8
      - Clang 6
      - MSVC 14.14
      - Xcode
      - R++
    keywords: ["CTAD"]

  - desc: "Concepts"
    paper: [P0734, P1616]
    summary: "Concepts are predicates that constrain template arguments. They provide clear error messages and enable function overloading based on type properties."
    support:
      - tool: GCC 5
        status: partial
        note: "TS-only"
      - GCC 10
      - Clang 10
      - MSVC 14.23
      - tool: Xcode 12
        status: partial
        note: "The following papers are not implemented: [P2103](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2103r0.html), DR1496, DR1734 and [P0848](https://wg21.link/P0848)."
      - R++
    ftm:
      - name: __cpp_concepts
        value: 201907L
    keywords: ["requires"]

  - desc: "Partial ordering of constrained function templates"
    paper: P2113
    support:
      - tool: GCC 10.2
        status: partial
        note: "Partial ordering of reversed comparison candidates is not implemented."
      - tool: Clang 16
        status: partial
        note: "Partial ordering of reversed comparison candidates is not implemented."

  - desc: "Return-type-requirements check the expression type against the concept"
    paper: P1084
    summary: "`{ E } -> C<Args...>;` in a requires-expression requires `C<decltype((E)), Args...>` to be satisfied instead of using template argument deduction."
    support:
      - GCC 10
      - tool: Clang 13
        note: "Clang 10 to 12 still use deduction semantics, so `{ t } -> Same<T&>;` is not satisfied for an lvalue `t` of type `T`."
      - MSVC 14.23

  - desc: "Remove the trailing-return-type form of return-type-requirements"
    paper: P1452
    summary: "`{ E } -> Type;` in a requires-expression is ill-formed. Use `{ E } -> std::convertible_to<Type>;` instead."
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.27

  - desc: "Disambiguating nested requirements"
    paper: P2092
    summary: "A requirement that starts with `requires` is always a nested-requirement, and `typename` is optional in requires-expression parameters."
    support:
      - GCC 10
      - Clang 16
      - MSVC 14.27

  - desc: "Check constraint satisfaction when forming a pointer to a function"
    paper: P1972
    summary: "Naming a function with unsatisfied constraints is ill-formed, including its address and `decltype` of its name."
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.27

  - desc: "Declaration matching for non-dependent requires-clauses"
    paper: P1980
    summary: "Trailing requires-clauses without template parameters match by expression equivalence, and concept definitions are treated as opaque."
    support:
      - GCC 10
      - Clang 10
      - tool: MSVC 14.23
        status: partial
        note: "Redeclarations whose requires-clauses differ only by an equivalent non-dependent expression, such as `C<42>` and `C<40 + 2>`, are not diagnosed."

  - desc: "Comparison rewrite fixes (\"spaceship tune-up\")"
    paper: P1630
    summary: "Rewritten relational candidates are chosen without checking the result of `<=>`, a selected rewritten `==` must return `bool`, and defaulted comparisons are deleted for reference and variant members."
    support:
      - tool: GCC 10
        note: "A SFINAE check for `!=` on a type whose `operator==` returns a class template specialization instantiates that class and can fail with a hard error."
      - Clang 10

  - desc: "Defaulted comparison specification fixes"
    paper: P2002
    summary: "Clarifies which declarations can be defaulted as comparison operators and the properties of defaulted comparisons, including the implicitly declared `operator==`."
    support:
      - GCC 10.2
      - Clang 17

  - desc: "Consistent defaulted comparisons"
    paper: P2085
    summary: "A defaulted comparison operator declared in a class can be defined outside the class."
    support:
      - GCC 10.2
      - Clang 14
      - MSVC 14.27

  - desc: "`std::endian`"
    paper: P0463
    lib: true
    support:
      - GCC 8
      - Clang 7
      - MSVC 14.22
      - Xcode 10

  - desc: "Extending `std::make_shared()` to support arrays"
    paper: P0674
    lib: true
    support:
      - GCC 12
      - Clang 15
      - MSVC 14.27
      - Xcode 14.3
    ftm:
      - name: __cpp_lib_shared_ptr_arrays
        value: 201707L

  - desc: "init-statements for range-based for"
    paper: P0614
    summary: "Add initialization to range-based for loops."
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.25
      - Xcode 11
      - R++

  - desc: "Simplifying implicit lambda capture"
    paper: P0588
    support:
      - GCC 8
      - MSVC 14.24
      - tool: R++
        status: unsupported
        issue: RSCPP-31582

  - desc: "ADL and function templates that are not visible"
    paper: P0846
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.21
      - Xcode 11.4
      - R++

  - desc: "`const` mismatch with defaulted copy constructor"
    paper: P0641
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.0
      - Xcode 10.2
      - R++

  - desc: "Specify when `constexpr` function definitions are needed for constant evaluation"
    paper: P0859
    support:
      - GCC 5.2 (partial)
      - GCC 9
      - Clang 8
      - MSVC 14.27 (partial)
      - MSVC 14.31
      - Xcode 11
    ftm:
      - name: __cpp_constexpr_in_decltype
        value: 201711L

  - desc: "Three-way comparison operator (`operator<=>`)"
    paper: [P0515, P0905]
    summary: 'The "spaceship operator" for simplified comparisons.'
    support:
      - GCC 10
      - Clang 8 (partial)
      - Clang 10
      - MSVC 14.20
      - Xcode 12
      - R++
    ftm:
      - name: __cpp_impl_three_way_comparison
        value: 201907L

  - desc: "Library support for `operator<=>` (`<compare>`)"
    paper: P0768
    lib: true
    support:
      - GCC 10
      - Clang 7 (partial)
      - Clang 12 (partial)
      - Clang 17
      - MSVC 14.20 (partial)
      - MSVC 14.28
      - Xcode 13
    ftm:
      - name: __cpp_lib_three_way_comparison
        value: 201907L

  - desc: "Fixing functionality gaps in constraints"
    paper: P0857
    support:
      - GCC 10
      - MSVC 14.23
      - Clang 16
      - Xcode 12
      - R++

  - desc: "Access checking on specializations"
    paper: P0692
    support:
      - GCC
      - Clang 8 (partial)
      - Clang 14
      - MSVC 14.26
      - Xcode 14
      - R++

  - desc: "Default constructible and assignable stateless lambdas"
    paper: P0624
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.22
      - Xcode 10.2
      - R++

  - desc: "Wording for lambdas in unevaluated contexts"
    paper: P0315
    support:
      - GCC 9
      - tool: Clang 13
        status: partial
        note: "Not supported: [temp.deduct/9]"
      - tool: Clang 14
        status: partial
        note: "temp.over.link changes"
      - Clang 17
      - MSVC 14.28
      - tool: Xcode 13.4.1
        status: partial
        note: "Not supported: [temp.deduct/9]"
      - R++

  - desc: "Transformation trait `std::remove_cvref`"
    paper: P0550
    lib: true
    support:
      - GCC 9
      - Clang 6
      - MSVC 14.20
      - Xcode 10
    ftm:
      - name: __cpp_lib_remove_cvref
        value: 201711L

  - desc: "`[[nodiscard]]` in the library"
    paper: P0600
    lib: true
    support:
      - GCC 9
      - Clang 7 (partial)
      - Clang 16
      - MSVC 14.13 (partial)
      - MSVC 14.22
      - Xcode 10 (partial)
      - Xcode 15

  - desc: "Make `std::memory_order` a scoped enumeration (`enum class`)"
    paper: P0439
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.25
      - Xcode 11.4

  - desc: "C++ Synchronized Buffered Ostream (`std::basic_osyncstream`)"
    paper: P0053
    lib: true
    support:
      - GCC 11
      - Clang 18
      - MSVC 14.29
    ftm:
      - name: __cpp_lib_syncbuf
        value: 201803L

  - desc: "Utility to convert a pointer to a raw pointer (`std::to_address()`)"
    paper: P0653
    lib: true
    support:
      - GCC 8
      - Clang 6
      - MSVC 14.22
      - Xcode
    ftm:
      - name: __cpp_lib_to_address
        value: 201711L

  - desc: "Add `constexpr` modifiers to functions in `<algorithm>` and `<utility>`"
    paper: P0202
    lib: true
    support:
      - GCC 10
      - Clang 8 (partial)
      - Clang 12
      - MSVC 14.26
      - Xcode 10.2 (partial)
      - Xcode 13
    ftm:
      - name: __cpp_lib_constexpr_algorithms
        value: 201806L

  - desc: "`constexpr` for `std::complex`"
    paper: P0415
    lib: true
    support:
      - GCC 9
      - Clang 7 (partial)
      - Clang 16
      - MSVC 14.27
      - Xcode 10 (partial)
      - Xcode 15
    ftm:
      - name: __cpp_lib_constexpr_complex
        value: 201711L

  - desc: "Atomic `std::shared_ptr` and `std::weak_ptr`"
    paper: P0718
    lib: true
    support: [GCC 12, MSVC 14.27]
    ftm:
      - name: __cpp_lib_atomic_shared_ptr
        value: 201711L

  - desc: "Floating Point Atomic"
    paper: P0020
    lib: true
    support:
      - GCC 10
      - Clang 18
      - MSVC 14.22
      - Xcode 16
    ftm:
      - name: __cpp_lib_atomic_float
        value: 201711L

  - desc: "Using `std::move()` in numeric algorithms"
    paper: P0616
    lib: true
    support:
      - GCC 9
      - Clang 12
      - MSVC 14.23
      - Xcode 13

  - desc: "String prefix and suffix checking: `std::string` and `std::string_view` `starts_with()` and `ends_with()`"
    paper: P0457
    lib: true
    support:
      - GCC 9
      - Clang 6
      - MSVC 14.21
      - Xcode 10
    ftm:
      - name: __cpp_lib_starts_ends_with
        value: 201711L

  - desc: "Language support for empty objects (`[[no_unique_address]]` attribute)"
    paper: P0840
    summary: "Allow empty class members to share address with other members."
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.28
      - Xcode 11.4
      - R++ 2023.2

  - desc: "Relaxing the range-`for` loop customization point finding rules"
    paper: P0962
    support:
      - GCC 8
      - Clang 8
      - MSVC 14.25
      - Xcode 11
      - R++

  - desc: "Allow structured bindings to accessible members"
    paper: P0969
    support:
      - GCC 8
      - Clang 8
      - MSVC 14.20
      - Xcode 10.2
      - R++

  - desc: "Relaxing the structured bindings customization point finding rules"
    paper: P0961
    support:
      - GCC 8
      - Clang 8
      - MSVC 14.20
      - Xcode 10.2
      - R++

  - desc: "Down with `typename`!"
    paper: P0634
    support:
      - GCC 9
      - Clang 16
      - MSVC 14.28
      - Xcode 16
      - R++ 2025.2

  - desc: "Pack-expansions in lambda init-captures"
    paper: [P0780, P2095]
    summary: "Capture parameter packs in lambda expressions."
    support:
      - tool: GCC 9
        note: "Reference pack init-captures are spelled `...&name = init`. The corrected `&...name = init` (P2095) is accepted from GCC 10, which rejects the old spelling."
      - Clang 9
      - MSVC 14.22
      - Xcode 11.4
      - R++
    ftm:
      - name: __cpp_init_captures
        value: 201803L

  - desc: "Attributes `[[likely]]` and `[[unlikely]]`"
    paper: P0479
    summary: "Hint to the compiler about branch probability."
    support:
      - GCC 9
      - Clang 12
      - MSVC 14.26
      - Xcode 13
      - R++

  - desc: "Symmetry for spaceship"
    paper: P0905
    lib: true
    support:
      - GCC 10
      - Clang 7
      - Xcode 16.3
      - MSVC

  - desc: "`<version>`"
    paper: P0754
    lib: true
    support:
      - GCC 9
      - Clang 7
      - MSVC 14.22
      - Xcode 10

  - desc: "Comparing unordered containers"
    paper: P0809
    lib: true
    support:
      - GCC
      - Clang
      - MSVC 10.0
      - Xcode

  - desc: "Extending `<chrono>` to calendars and time zones"
    paper: P0355
    lib: true
    support:
      - GCC 11 (partial)
      - GCC 13 (partial)
      - GCC 14
      - tool: Clang 8
        status: partial
        note: "Supports calendar types and the `sys_time`/`local_time` aliases; parsing and time-zone support are not implemented."
      - tool: Clang 19
        status: partial
        note: "Adds the time-zone database and `std::chrono::zoned_time`, requiring `-fexperimental-library`. Parsing remains unimplemented."
      - tool: Clang 20
        status: partial
        note: "In addition to Clang 19, supports `std::chrono::utc_clock`. Parsing remains unimplemented."
      - tool: Clang 21
        status: partial
        note: "In addition to Clang 20, supports `std::chrono::tai_clock` and `std::chrono::gps_clock`. Parsing remains unimplemented."
      - MSVC 14.29
      - Xcode 10 (partial)
    ftm:
      - name: __cpp_lib_chrono
        value: 201907L
    keywords: ["std::chrono::year_month_day", "std::chrono::zoned_time", "tzdb"]

  - desc: "`std::basic_string::reserve()` should not shrink"
    paper: P0966
    lib: true
    support:
      - GCC 11
      - Clang 12
      - MSVC 14.25
      - Xcode

  - desc: "`std::span`"
    paper: P0122
    lib: true
    support:
      - GCC 10
      - Clang 7
      - MSVC 14.26
      - Xcode 10
    ftm:
      - name: __cpp_lib_span
        value: 201803L

  - desc: "[ConstexprIterator](https://cppreference.com/cpp/named_req/ConstexprIterator) requirements"
    paper: P0858
    lib: true
    support:
      - GCC 9
      - Clang 12
      - MSVC 14.11
      - Xcode 13
    ftm:
      - name: __cpp_lib_string_view
        value: 201803L
      - name: __cpp_lib_array_constexpr
        value: 201811L

  - desc: "Deprecate implicit capture of this via `[=]`"
    paper: P0806
    support:
      - GCC 9
      - Clang 7
      - MSVC 14.22
      - Xcode 10.2
      - tool: R++
        status: unsupported
        issue: RSCPP-31582
    keywords:
      - lambda

  - desc: "Class types in non-type template parameters"
    paper: P0732
    support:
      - GCC 9
      - Clang 12
      - MSVC 14.26 (partial)
      - MSVC 14.28
      - Xcode 13 (partial)
      - Xcode 16.3
      - R++ 2021.3
    keywords: ["NTTP"]

  - desc: "Atomic compare-and-exchange with padding bits"
    paper: P0528
    lib: true
    support: [GCC 13, Clang 24, MSVC 14.28]

  - desc: "Destroying operator delete"
    paper: P0722
    summary: "Custom deallocation with access to the object."
    support:
      - GCC 9
      - Clang 6
      - MSVC 14.27
      - Xcode 10
      - tool: R++
        status: unsupported
        issue: RSCPP-37872
    ftm:
      - name: __cpp_impl_destroying_delete
        value: 201806L

  - desc: "`std::destroying_delete_t`"
    paper: P0722
    summary: "Custom deallocation with access to the object."
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.27
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_destroying_delete
        value: 201806L

  - desc: "Allowing virtual function calls in constant expressions"
    paper: P1064
    support:
      - tool: GCC 9
        note: "GCC 9.1 and 9.2 do not evaluate virtual function calls in constant expressions. This is fixed in GCC 9.3."
      - Clang 9
      - MSVC 14.28
      - Xcode 11.4
      - R++ 2021.3
    ftm:
      - name: __cpp_constexpr
        value: 201907L
    keywords:
      - constexpr

  - desc: "Prohibit aggregates with user-declared constructors"
    paper: P1008
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.20
      - Xcode 10.2
      - R++

  - desc: "Consistency improvements for comparisons"
    paper: P1120
    support:
      - GCC 10
      - Clang 8 (partial)
      - Clang 10
      - MSVC 14.22
      - Xcode 12
      - tool: R++
        status: unsupported

  - desc: "Integrating feature-test macros"
    paper: P0941
    support:
      - GCC 5
      - Clang 3.4
      - MSVC 14.15 (partial)
      - MSVC 14.20
      - Xcode
      - R++

  - desc: "`explicit(bool)`"
    paper: P0892
    summary: "Conditionally explicit constructors and conversions."
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.24
      - Xcode 11.4
      - R++
    ftm:
      - name: __cpp_conditional_explicit
        value: 201806L

  - desc: "Guaranteed copy elision for piecewise construction"
    paper: P0475
    lib: true
    support:
      - GCC 9
      - Clang
      - MSVC 14.29
      - Xcode

  - desc: "`std::bit_cast()`"
    paper: P0476
    lib: true
    support:
      - GCC 11
      - Clang 14
      - MSVC 14.27
      - Xcode 14.3
    ftm:
      - name: __cpp_lib_bit_cast
        value: 201806L
    keywords: ["<bit>"]

  - desc: "`contains()` member function of associative containers, e.g. `std::map::contains()`"
    paper: P0458
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.21
      - Xcode 13.4.1

  - desc: "`constexpr` comparison operators for `std::array`"
    paper: P1023
    lib: true
    support:
      - GCC 10
      - Clang 8
      - MSVC 14.27
      - Xcode 10.2

  - desc: "Add `std::shift_left()` and `std::shift_right()` to `<algorithm>`"
    paper: P0769
    lib: true
    support:
      - GCC 10
      - tool: Clang 12
        status: partial
        note: "The parallel versions (`std::execution::par`) are not implemented yet. ([Issue](https://github.com/llvm/llvm-project/issues/104095))"
      - MSVC 14.21
      - tool: Xcode 13
        status: partial
        note: "The parallel versions (`std::execution::par`) are not implemented yet. ([Issue](https://github.com/llvm/llvm-project/issues/104095))"
    ftm:
      - name: __cpp_lib_shift
        value: 201806L

  - desc: "`std::type_identity`"
    paper: P0887
    lib: true
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.21
      - Xcode 10.2
    ftm:
      - name: __cpp_lib_type_identity
        value: 201806L

  - desc: "`constexpr` for `std::swap()` and swap related functions"
    paper: P0879
    lib: true
    support:
      - GCC 10
      - Clang 13
      - MSVC 14.26
      - Xcode 13.4.1

  - desc: "`std::is_convertible`"
    paper: P0758
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.23
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_is_nothrow_convertible
        value: 201806L

  - desc: "Integral power-of-2 operations: `std::bit_ceil()`, `std::bit_floor()`, `std::bit_width()`, `std::has_single_bit()`"
    paper: [P0556, P1956]
    lib: true
    support:
      - GCC 9
      - GCC 10
      - Clang 9
      - Clang 12
      - MSVC 14.28
      - Xcode 11.4
      - Xcode 13
    ftm:
      - name: __cpp_lib_int_pow2
        value: 202002L
    keywords: ["<bit>"]

  - desc: "`std::atomic_ref`"
    paper: P0019
    lib: true
    support:
      - GCC 10
      - Clang 19
      - MSVC 14.28
      - Xcode 16.3
    ftm:
      - name: __cpp_lib_atomic_ref
        value: 201806L

  - desc: "Improving the return value of erase-like algorithms"
    paper: P0646
    lib: true
    support:
      - GCC 9
      - Clang 10
      - MSVC 14.21
      - Xcode 12
    ftm:
      - name: __cpp_lib_list_remove_return_type
        value: 201806L

  - desc: "Reviewing deprecated facilities of C++17 for C++20"
    paper: P0619
    lib: true
    support:
      - GCC 12
      - MSVC 14.26
      - tool: Clang 20
        note: "Removed headers are still provided as an extension, but with deprecation warnings."
      - Xcode 26

  - desc: "Concepts library"
    paper: P0898
    lib: true
    support:
      - GCC 10
      - Clang 13
      - MSVC 14.23
      - Xcode 13.4.1
    ftm:
      - name: __cpp_lib_concepts
        value: 202002L
    keywords: ["<concepts>", "std::same_as", "std::convertible_to"]

  - desc: "`constexpr` try-catch blocks"
    paper: P1002
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.25
      - Xcode 10.2
      - R++ 2026.2

  - desc: "`dynamic_cast` and polymorphic `typeid` in constant expressions"
    paper: P1327
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.28
      - Xcode 11.4
      - tool: R++
        status: unsupported
        issue: RSCPP-37873

  - desc: "Signed integers are two's complement"
    paper: P1236
    summary: "Signed integers are guaranteed to use two's complement representation."
    support:
      - GCC 9
      - Clang 9
      - MSVC
      - Xcode 11.4
      - R++

  - desc: "`char8_t`: A type for UTF-8 characters and strings"
    paper: P0482
    summary: "A distinct type for UTF-8 encoded characters and strings."
    support:
      - GCC 9
      - Clang 7
      - MSVC 14.22
      - Xcode 10
      - R++
    ftm:
      - name: __cpp_char8_t
        value: 201811L

  - desc: "Library support for `char8_t`"
    paper: P0482
    summary: "A distinct type for UTF-8 encoded characters and strings."
    lib: true
    support:
      - GCC 9
      - Clang 8 (partial)
      - Clang 16
      - MSVC 14.22
      - Xcode 10.2 (partial)
      - Xcode 15
    ftm:
      - name: __cpp_lib_char8_t
        value: 201907L

  - desc: "Missing feature test macros"
    paper: P1353
    support:
      - tool: GCC 9
        status: partial
        note: "Defines the destroying delete and conditional explicit macros. The three-way comparison macros are defined from GCC 10."
      - GCC 10
      - tool: Clang 9
        status: partial
        note: "Defines the destroying delete and conditional explicit macros. `__cpp_impl_three_way_comparison` is defined from Clang 10 and libc++ defines `__cpp_lib_three_way_comparison` from Clang 19."
      - Clang 19
      - MSVC 14.29
      - Xcode
      - R++

  - desc: "Immediate functions (`consteval`)"
    paper: [P1073, P1937]
    summary: "Functions that must be evaluated at compile time."
    support:
      - tool: GCC 10
        status: partial
        note: "`consteval` virtual functions are not supported."
      - GCC 11
      - Clang 11 (partial)
      - tool: Clang 14
        status: partial
        note: "P1937 is implemented, but other immediate-function support and the feature-test macro are incomplete."
      - Clang 17
      - MSVC 14.28 (partial)
      - MSVC 14.29
      - tool: Xcode 15
        status: partial
        note: "Apple lists the complete feature for Xcode 16.3. Xcode 15 predates the complete upstream Clang implementation (Clang 17)."
      - Xcode 16.3
      - R++
    ftm:
      - name: __cpp_consteval
        value: 201811L

  - desc: "`std::is_constant_evaluated()`"
    paper: P0595
    summary: "Detect if code is running at compile time or runtime."
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.25
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_is_constant_evaluated
        value: 201811L

  - desc: "Yet another approach for constrained declarations"
    paper: P1141
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.26 (partial)
      - MSVC 14.28
      - Xcode 12.5
      - R++

  - desc: "Nested inline namespaces"
    paper: P1094
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.27
      - Xcode 10.2
      - R++

  - desc: "Changing the active member of a `union` inside `constexpr`"
    paper: P1330
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.10
      - Xcode 10.3
      - R++
    ftm:
      - name: __cpp_constexpr
        value: 202002L

  - desc: "Fixing `operator>>(basic_istream&, CharT*)`"
    paper: P0487
    lib: true
    support:
      - GCC 11
      - Clang 8
      - MSVC 14.23
      - Xcode 10.2

  - desc: "`std::variant` and `std::optional` should propagate copy/move triviality"
    paper: P0602
    lib: true
    support:
      - GCC 8.3
      - Clang 8
      - MSVC 14.11
      - Xcode 10.2

  - desc: "`<chrono>` `zero()`, `min()` and `max()` should be `noexcept`"
    paper: P0972
    lib: true
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.14
      - Xcode 10.2

  - desc: "`constexpr` in `std::pointer_traits`"
    paper: P1006
    lib: true
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.26
      - Xcode 10.2
    ftm:
      - name: __cpp_lib_constexpr_memory
        value: 201811L

  - desc: "Misc `constexpr` bits"
    paper: P1032
    lib: true
    support:
      - GCC 10
      - Clang 13
      - MSVC 14.28
      - Xcode 13.4.1
    ftm:
      - name: __cpp_lib_array_constexpr
        value: 201811L
      - name: __cpp_lib_constexpr_functional
        value: 201907L
      - name: __cpp_lib_constexpr_iterator
        value: 201811L
      - name: __cpp_lib_constexpr_tuple
        value: 201811L
      - name: __cpp_lib_constexpr_utility
        value: 201811L
      - name: __cpp_lib_constexpr_string_view
        value: 201811L

  - desc: "`std::unwrap_ref_decay` and `std::unwrap_reference`"
    paper: P0318
    lib: true
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.21
      - Xcode 10.2
    ftm:
      - name: __cpp_lib_unwrap_ref
        value: 201811L

  - desc: "`std::reference_wrapper` for incomplete types"
    paper: P0357
    lib: true
    support:
      - GCC 9
      - Clang 8
      - MSVC 14.26
      - Xcode 10.2

  - desc: "A sane `std::variant` converting constructor"
    paper: P0608
    lib: true
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.29
      - MSVC 14.42
      - Xcode 11.4

  - desc: "`std::function`'s move constructor should be `noexcept`"
    paper: P0771
    lib: true
    support:
      - GCC 7.2
      - Clang 6
      - MSVC 14.22
      - Xcode

  - desc: "`std::assume_aligned()`"
    paper: P1007
    lib: true
    support:
      - GCC 9
      - GCC 11
      - Clang 15
      - MSVC 14.28
      - Xcode 14.3
    ftm:
      - name: __cpp_lib_assume_aligned
        value: 201811L

  - desc: "Smart pointer creation with default initialization (e.g. `std::make_unique_for_overwrite()`)"
    paper: [P1020, P1973]
    lib: true
    support:
      - GCC 11
      - GCC 12
      - Clang 16
      - MSVC 14.28
      - Xcode 15
    ftm:
      - name: __cpp_lib_smart_ptr_for_overwrite
        value: 202002L

  - desc: "Utility functions to implement uses-allocator construction"
    paper: P0591
    lib: true
    support:
      - GCC 9
      - Clang 16
      - MSVC 14.29
      - Xcode 15
    keywords:
      [
        "std::make_obj_using_allocator",
        "std::uses_allocator_construction_args",
      ]

  - desc: "Remove comparison operators of `std::span`"
    paper: P1085
    lib: true
    support:
      - GCC 10
      - Clang 8
      - MSVC 14.26
      - Xcode 10.2

  - desc: "Make stateful allocator propagation more consistent for `operator+(basic_string)`"
    paper: P1165
    lib: true
    support:
      - GCC 10
      - Clang 15
      - MSVC 14.26
      - Xcode 14.3

  - desc: "The One Ranges Proposal"
    paper: P0896
    lib: true
    support:
      - GCC 10
      - Clang 13 (partial)
      - tool: Clang 15
        status: partial
        note: "`views::elements`, `views::keys`, `views::values`, `views::split` and `views::lazy_split` are missing."
      - Clang 16
      - MSVC 14.29
      - tool: Xcode 14.3
        status: partial
        note: "`views::elements`, `views::keys`, `views::values`, `views::split` and `views::lazy_split` are missing."
      - Xcode 15
    ftm:
      - name: __cpp_lib_ranges
        value: 201911L
    keywords:
      [
        "<ranges>",
        "std::views",
        "views::filter",
        "views::transform",
        "views::take",
        "views::drop",
        "views::reverse",
      ]

  - desc: "`std::bind_front()`"
    paper: [P0356, P1651]
    lib: true
    support:
      - tool: GCC 9
        note: "GCC 9.1 and 9.2 unwrap `std::reference_wrapper` arguments instead of passing them as is (P1651). This is fixed in GCC 9.3."
      - Clang 13
      - MSVC 14.25
      - Xcode 13.4.1
    ftm:
      - name: __cpp_lib_bind_front
        value: 201907L

  - desc: "Remove unnecessarily explicit default constructors"
    paper: P0935
    summary: "Random number engines, distributions and `random_device`, and string streams and `std::stringbuf` can be initialized from `{}`."
    lib: true
    support:
      - GCC 9
      - Clang 12
      - MSVC 14.26

  - desc: "Heterogeneous lookup for unordered associative containers"
    paper: [P0919, P1690]
    lib: true
    support:
      - GCC 11
      - Clang 12
      - MSVC 14.23
      - MSVC 14.25
      - Xcode 13
    ftm:
      - name: __cpp_lib_generic_unordered_lookup
        value: 201811L
    keywords: ["is_transparent"]

  - desc: "Consistent container erasure (`std::erase()` and `std::erase_if()`)"
    paper: [P1209, P1115]
    lib: true
    support:
      - GCC 9
      - GCC 10
      - Clang 8
      - Clang 11
      - MSVC 14.25
      - MSVC 14.27
      - Xcode 10.2
      - Xcode 12.5
    ftm:
      - name: __cpp_lib_erase_if
        value: 202002L

  - desc: "Explicitly defaulted functions with different exception specifications"
    paper: P1286
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.28
      - Xcode 11.4

  - desc: "Structured binding extensions"
    paper: [P1091, P1381]
    support:
      - GCC 10
      - Clang 8 (partial)
      - Clang 16
      - MSVC 14.11
      - MSVC 14.24
      - Xcode 16
      - R++

  - desc: "Stronger Unicode requirements"
    paper: [P1041, P1139]
    support:
      - GCC 10
      - Clang
      - MSVC 14.26
      - Xcode

  - desc: "Parenthesized initialization of aggregates"
    paper: [P0960, P1975]
    support:
      - GCC 10
      - Clang 16
      - MSVC 14.28
      - Xcode 16
      - R++
    ftm:
      - name: __cpp_aggregate_paren_init
        value: 201902L

  - desc: "Array size deduction in `new`-expressions"
    paper: P1009
    support:
      - GCC 11
      - Clang 9
      - MSVC 14.27
      - Xcode 11.4
      - R++

  - desc: "Modules"
    paper: [P1103, P1703, P1766, P1779, P1811, P1815, P1857, P1874, P1979, P2115, P2615, P2788]
    summary: "Modern alternative to header files with better encapsulation and faster builds."
    support:
      - tool: GCC 11
        status: partial
        note: "Supports the majority of modules features, except for P1815, private module fragments, parser-level global module entity merging and global module implications of `extern \\\"C/C++\\\"` (P1103)."
      - tool: GCC 15
        status: partial
        note: "In addition to GCC 11, supports P2615. Private module fragments, partition definition visibility rules and textual merging of reachable global module entities remain unimplemented."
      - tool: GCC 16
        status: partial
        note: "In addition to GCC 15, supports P1766 and P1815. Private module fragments, partition definition visibility rules and textual merging of reachable global module entities remain unimplemented."
      - tool: Clang 17
        status: partial
        note: "Supports the majority of modules features, except for P1857, and P1815 is supported on all targets except Windows."
      - tool: Clang 21
        status: partial
        note: "In addition to Clang 17, partially supports P1857, with the following note: _The restriction that '[a] module directive may only appear as the first preprocessing tokens in a file' is enforced starting in Clang 21._"
      - tool: Clang 23
        status: partial
        note: "In addition to Clang 21, supports P1857."
      - MSVC 14.0 (partial)
      - MSVC 14.28
      - tool: Xcode 26
        note: "Apple Clang requires the `-fcxx-modules` flag **in addition to** `-fmodules`.<br/><br/> Xcode 26 does not ship the `clang-scan-deps` utility that is required by certain build system generators like CMake, in order to scan module dependencies.<br/> This means that C++ modules cannot be used in conjunction with CMake's Xcode generator (`-G Xcode`).\n"
      - R++
    ftm:
      - name: __cpp_modules
        value: 201907L
    keywords: ["import", "export"]

  - desc: "`<=>` `!=` `==`"
    paper: P1185
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.22
      - Xcode 12
      - R++

  - desc: "Coroutines"
    paper: [P0912, LWG3393]
    summary: "Suspendable functions for async programming and generators."
    support:
      - tool: GCC 10
        note: "Requires `-fcoroutines`. Starting with GCC 11, this is implicitly enabled by `-std=c++20`."
      - Clang 8 (partial)
      - tool: Clang 17
        status: partial
        note: "Fully supported on all targets except Windows, which still has some stability and ABI issues."
      - MSVC 14.0 (partial)
      - MSVC 14.10
      - MSVC 14.28
      - Xcode 10.2 (partial)
      - Xcode 16.3
      - R++
    ftm:
      - name: __cpp_impl_coroutine
        value: 201902L
      - name: __cpp_lib_coroutine
        value: 201902L
    keywords: ["co_await", "co_yield", "co_return", "<coroutine>"]

  - desc: "`pmr::polymorphic_allocator<>` as a vocabulary type"
    paper: P0339
    lib: true
    support:
      - GCC 9
      - Clang 16
      - MSVC 14.28
      - Xcode 15
    ftm:
      - name: __cpp_lib_polymorphic_allocator
        value: 201902L

  - desc: "Make `filesystem::create_directory()` intuitive"
    paper: P1164
    lib: true
    support:
      - GCC 8.3
      - Clang 12
      - MSVC 14.20
      - Xcode 13

  - desc: "`std::lerp()` and `std::midpoint()`"
    paper: P0811
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.23
      - MSVC 14.28
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_interpolate
        value: 201902L

  - desc: "Target Vectorization Policies from Parallelism V2 TS to C++20 (`std::execution::unseq`)"
    paper: P1001
    lib: true
    support:
      - tool: GCC 9
        note: "`<execution>` includes Intel TBB headers, so they must be installed to compile. From GCC 10, `<execution>` compiles without TBB."
      - tool: Clang 17
        note: "Not supported by Clang on macOS."
      - MSVC 14.28
    ftm:
      - name: __cpp_lib_execution
        value: 201902L

  - desc: "`std::ssize()` and unsigned extent for `std::span`"
    paper: P1227
    lib: true
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.25
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_ssize
        value: 201902L

  - desc: "Usability enhancements for `std::span`"
    paper: P1024
    lib: true
    support:
      - GCC 10
      - Clang 9
      - Clang 14
      - MSVC 14.26
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_span
        value: 201902L

  - desc: "`std::span::size_type` replaces `index_type`"
    paper: P1872
    lib: true
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.26

  - desc: "Range constructor for `std::span`"
    paper: P1394
    summary: "`std::span` is constructible from contiguous iterator pairs and contiguous ranges, with deduction guides for both."
    lib: true
    support:
      - GCC 10
      - tool: Clang 14
        status: partial
        note: "libc++ 14 has the iterator constructors, but not the range constructor or the deduction guide for ranges."
      - Clang 15
      - MSVC 14.26

  - desc: "Fixed-size `std::span` construction from a dynamic range"
    paper: P1976
    summary: "Constructing a `std::span` with a static extent from a span or range with a dynamic extent is `explicit`."
    lib: true
    support:
      - GCC 10
      - Clang 11
      - MSVC 14.27
    ftm:
      - name: __cpp_lib_span
        value: 202002L

  - desc: "Traits for (un)bounded arrays"
    paper: P1357
    lib: true
    support:
      - GCC 9
      - Clang 9
      - MSVC 14.25
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_bounded_array_traits
        value: 201902L
    keywords: ["std::is_bounded_array", "std::is_unbounded_array"]

  - desc: "Deprecate comma operator in subscripts"
    paper: P1161
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.25
      - Xcode 11.4
      - tool: R++
        status: unsupported
        issue: RSCPP-31583

  - desc: "Permitting trivial default initialization in `constexpr` contexts"
    paper: P1331
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.27
      - Xcode 12
      - R++ 2025.1

  - desc: "Conditionally trivial special member functions"
    paper: P0848
    support:
      - tool: GCC 10
        note: "`__cpp_concepts` reports 202002L from GCC 12."
      - tool: Clang 16
        note: "Handling of deleted special member functions does not follow DR1496 and DR1734. `__cpp_concepts` reports 202002L from Clang 19."
      - MSVC 14.28
      - Xcode 16.3
      - R++
    ftm:
      - name: __cpp_concepts
        value: 202002L

  - desc: "Synthesizing Three-way comparison for specified comparison category"
    paper: P1186
    support:
      - GCC 11
      - Clang 10
      - MSVC 14.24
      - Xcode 12

  - desc: '`[[nodiscard("should have a reason")]]`'
    paper: P1301
    summary: "Add explanation to [[nodiscard]] warnings."
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.25
      - Xcode 11.4
      - R++ 2022.3

  - desc: "`using` enum"
    paper: P1099
    summary: "Import enum members into the current scope."
    support:
      - GCC 11
      - Clang 13
      - MSVC 14.24
      - Xcode 13.4.1
      - R++
    ftm:
      - name: __cpp_using_enum
        value: 201907L

  - desc: "Class template argument deduction for aggregates"
    paper: [P1816, P2082]
    support:
      - GCC 10
      - GCC 11
      - Clang 17
      - MSVC 14.27
      - R++ 2021.3
    ftm:
      - name: __cpp_deduction_guides
        value: 201907L
    keywords: ["CTAD"]

  - desc: "Unevaluated `asm`-declaration in `constexpr` functions"
    paper: P1668
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.28
      - Xcode 12
      - R++

  - desc: "Permit conversions to arrays of unknown bound"
    paper: P0388
    support:
      - GCC 10
      - Clang 14
      - MSVC 14.27
      - Xcode 14
      - tool: R++
        status: unsupported
        issue: RSCPP-37874

  - desc: "`constinit`"
    paper: P1143
    summary: "Ensure static/thread-local variables are constant-initialized."
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.29
      - Xcode 12
      - R++
    ftm:
      - name: __cpp_constinit
        value: 201907L

  - desc: "Deprecating some uses of `volatile`"
    paper: P1152
    summary: "Certain volatile operations are deprecated."
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.27
      - Xcode 12

  - desc: "`[[nodiscard]]` for constructors"
    paper: P1771
    support:
      - GCC 10
      - Clang 9
      - MSVC 14.24
      - Xcode 11.4
      - R++

  - desc: "Class template argument deduction for alias templates"
    paper: P1814
    support:
      - GCC 10
      - tool: Clang 19
        status: partial
        note: "This feature has been initially completed, but the feature macro `__cpp_deduction_guides` has not been updated."
      - MSVC 14.27
      - R++
    ftm:
      - name: __cpp_deduction_guides
        value: 201907L
    keywords: ["CTAD"]

  - desc: "Implicit move for more local objects and rvalue references"
    paper: [P1825, P0527, P1155]
    support:
      - GCC 11
      - Clang 13
      - MSVC 14.24
      - Xcode 13.4.1
      - tool: R++
        status: partial
        issue: RSCPP-37266
        note: "The implicit move from an rvalue reference is not implemented."

  - desc: "`constexpr` container operations"
    paper: P0784
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.28
      - Xcode 12
      - R++
    ftm:
      - name: __cpp_constexpr_dynamic_alloc
        value: 201907L
    keywords: ["constexpr new"]

  - desc: "`constexpr` `std::allocator` and related utilities"
    paper: P0784
    lib: true
    support:
      - GCC 10
      - Clang 12
      - tool: MSVC 14.28
        status: partial
        note: "`std::allocator` and `std::construct_at()` work in constant expressions, but the feature-test macro is defined from MSVC 14.29."
      - MSVC 14.29
      - Xcode 13
    ftm:
      - name: __cpp_lib_constexpr_dynamic_alloc
        value: 201907L
    keywords: ["std::construct_at", "std::destroy_at"]

  - desc: "Bit operations: `std::rotl()`, `rotr()`, `countl_zero()`, `countl_one()`, `countr_zero()`, `countr_one()`, `popcount()`"
    paper: P0553
    lib: true
    support:
      - tool: GCC 9
        note: "GCC 9.1 lacks the functions, which are available from GCC 9.2. `__cpp_lib_bitops` is defined from GCC 9.4."
      - Clang 9
      - MSVC 14.25
      - MSVC 14.28
      - Xcode 11.4
    ftm:
      - name: __cpp_lib_bitops
        value: 201907L
    keywords: ["<bit>"]

  - desc: "`std::format()`"
    paper: P0645
    lib: true
    support:
      - GCC 13
      - tool: Clang 14
        status: partial
        note: "Incomplete. Available only when libc++ is built with `LIBCXX_ENABLE_INCOMPLETE_FEATURES`."
      - tool: Clang 15
        status: partial
        note: "Incomplete. Requires `-fexperimental-library`."
      - Clang 17
      - MSVC 14.29
      - Xcode 15.3
    ftm:
      - name: __cpp_lib_format
        value: 201907L
    keywords: ["<format>", "std::formatter", "std::format_to", "std::vformat"]

  - desc: "Integration of chrono with text formatting"
    paper: P1361
    lib: true
    support:
      - GCC 13
      - Clang 21
      - MSVC 14.29
      - Xcode 26.4

  - desc: "Mathematical constants"
    paper: P0631
    lib: true
    support:
      - GCC 10
      - Clang 11
      - MSVC 14.25
      - Xcode 12.5
    ftm:
      - name: __cpp_lib_math_constants
        value: 201907L
    keywords: ["std::numbers", "std::numbers::pi", "<numbers>"]

  - desc: "Atomic waiting and notifying, `std::counting_semaphore`, `std::latch` and `std::barrier`"
    paper: P1135
    lib: true
    support:
      - GCC 11
      - Clang 11
      - MSVC 14.28
      - tool: Xcode 13.4.1
        note: "Minimum deployment target: macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0"
    ftm:
      - name: __cpp_lib_atomic_flag_test
        value: 201907L
      - name: __cpp_lib_atomic_lock_free_type_aliases
        value: 201907L
      - name: __cpp_lib_atomic_wait
        value: 201907L
      - name: __cpp_lib_barrier
        value: 201907L
      - name: __cpp_lib_latch
        value: 201907L
      - name: __cpp_lib_semaphore
        value: 201907L

  - desc: "`std::atomic_ref::wait()`, `std::atomic_ref::notify_one()` and `std::atomic_ref::notify_all()`"
    paper: P1643
    lib: true
    support:
      - GCC 11
      - Clang 19
      - Xcode 16.3
      - MSVC 14.28

  - desc: "The Mothership has Landed: Adding `<=>` to the Library"
    paper: P1614
    lib: true
    support:
      - GCC 10
      - Clang 19
      - MSVC 14.29
      - Xcode 16.3
    ftm:
      - name: __cpp_lib_three_way_comparison
        value: 201907L

  - desc: "`std::to_array()`"
    paper: P0325
    lib: true
    support:
      - GCC 10
      - Clang 11
      - MSVC 14.25
      - Xcode
    ftm:
      - name: __cpp_lib_to_array
        value: 201907L

  - desc: "Efficient access to `std::basic_stringbuf`'s buffer"
    paper: P0408
    lib: true
    support:
      - GCC 11
      - Clang 17
      - MSVC 14.29
      - Xcode 15

  - desc: "`char8_t` backward compatibility remediation"
    paper: P1423
    lib: true
    support:
      - GCC 10
      - Clang 15
      - Xcode 14.3
      - MSVC 14.26
    ftm:
      - name: __cpp_lib_char8_t
        value: 201907L

  - desc: "Standard library header units"
    paper: P1502
    lib: true
    support:
      - GCC 11
      - tool: Clang 15
        status: partial
        note: "Experimental support requires manually precompiling headers and passing each BMI with `-fmodule-file`. Some combinations of header units fail to merge declarations in Clang 15, including `<vector>` with `<iostream>`."
      - MSVC 14.29

  - desc: "Output `chrono::days` with 'd' suffix"
    paper: P1650
    lib: true
    support:
      - GCC 13
      - Clang 16
      - MSVC 14.29
      - Xcode 15

  - desc: "`constexpr` `std::invoke()` and related utilities"
    paper: P1065
    lib: true
    support:
      - GCC 10
      - Clang 12
      - MSVC 14.28
      - Xcode 13
    ftm:
      - name: __cpp_lib_constexpr_functional
        value: 201907L

  - desc: "Input range adaptors"
    paper: P1035
    lib: true
    support:
      - GCC 10
      - Clang 16
      - MSVC 14.29
      - Xcode 15
    keywords:
      [
        "views::take_while",
        "views::drop_while",
        "views::elements",
        "views::keys",
        "views::values",
        "views::istream",
      ]

  - desc: "`ranges::basic_istream_view::iterator` should not be copyable"
    paper: P1638
    lib: true
    support:
      - GCC 11
      - Clang 16
      - Xcode 15
      - MSVC 14.29

  - desc: "`constexpr` `std::vector`"
    paper: P1004
    lib: true
    support:
      - GCC 12
      - Clang 15
      - MSVC 14.29
      - MSVC 14.30
      - Xcode 14.3
    ftm:
      - name: __cpp_lib_constexpr_vector
        value: 201907L

  - desc: "`std::stop_token` and `std::jthread`"
    paper: P0660
    lib: true
    support:
      - GCC 10
      - tool: Clang 17
        status: partial
        note: "Guarded behind compiler flag `-fexperimental-library`."
      - Clang 20
      - tool: MSVC 14.28
        note: "MSVC 14.28 is available with VS 16.8 and VS 16.9. This feature is supported starting with VS 16.9, which is identifiable by checking `_MSC_FULL_VER == 192829910`."
      - tool: Xcode 16.4
        status: partial
        note: "Guarded behind compiler flag `-fexperimental-library`."
      - Xcode 26
    ftm:
      - name: __cpp_lib_jthread
        value: 201911L

  - desc: "Layout-compatibility and pointer-interconvertibility traits"
    paper: P0466
    lib: true
    support: [GCC 12, MSVC 14.29]
    ftm:
      - name: __cpp_lib_is_layout_compatible
        value: 201907L
      - name: __cpp_lib_is_pointer_interconvertible
        value: 201907L
    keywords:
      [
        "std::is_layout_compatible",
        "std::is_pointer_interconvertible_base_of",
        "std::is_corresponding_member",
      ]

  - desc: "`std::source_location`"
    paper: P1208
    lib: true
    support:
      - GCC 11
      - Clang 16
      - MSVC 14.29
      - Xcode 15
    ftm:
      - name: __cpp_lib_source_location
        value: 201907L

  - desc: "Allow defaulting comparisons by value"
    paper: P1946
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.25
      - Xcode 12
      - R++

  - desc: "Inconsistencies with constant template parameters"
    paper: P1907
    support:
      - GCC 10 (partial)
      - GCC 11
      - tool: Clang 18
        status: partial
        note: "Reference template arguments referring to instantiation-dependent objects and subobjects are not fully supported."
      - MSVC 14.26
      - Xcode 13.4.1 (partial)
      - R++
    ftm:
      - name: __cpp_nontype_template_args
        value: 201911L

  - desc: "Concept traits should be named after concepts"
    paper: P1871
    lib: true
    support:
      - GCC 10
      - Clang 14
      - Xcode
      - MSVC 14.27

  - desc: "Ranges adaptors for non-copyable iterators"
    paper: P1862
    lib: true
    support:
      - GCC 10
      - Clang 16
      - Xcode 15
      - MSVC 14.29

  - desc: "Add `max()` to latch and barrier"
    paper: P1865
    lib: true
    support:
      - GCC 11
      - Clang 11
      - MSVC 14.28
      - tool: Xcode
        note: "Minimum deployment target: macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0"

  - desc: "`constexpr` default constructor of `std::atomic` and `std::atomic_flag`"
    paper: P0883
    lib: true
    support:
      - GCC 10
      - Clang 13
      - MSVC 14.26
      - Xcode 13.4.1
    ftm:
      - name: __cpp_lib_atomic_value_initialization
        value: 201911L

  - desc: "Remove `std::weak_equality` and `std::strong_equality`"
    paper: P1959
    lib: true
    support:
      - GCC 10
      - Clang 10
      - MSVC 14.25
      - Xcode 12
      - R++

  - desc: "`constexpr` for numeric algorithms"
    paper: P1645
    lib: true
    support:
      - GCC 10
      - Clang 12
      - MSVC 14.26
      - Xcode 13
    ftm:
      - name: __cpp_lib_constexpr_numeric
        value: 201911L

  - desc: "Pseudo-destructors end object lifetimes"
    paper: P0593
    support:
      - GCC 11
      - Clang 11
      - MSVC
      - Xcode 12.5
      - R++
    keywords: ["implicit lifetime"]

  - desc: "Checking for abstract class types"
    paper: P0929
    summary: "Abstract parameter and return types are diagnosed at function definitions and calls instead of at declarations."
    support:
      - GCC 11
      - tool: Clang 17
        status: partial
        note: "Calls to functions returning an abstract class type are not diagnosed."

  - desc: "Converting from `T*` to `bool` should be considered narrowing"
    paper: P1957
    support:
      - tool: GCC 10
        note: "In C++20 mode only. (`-std=c++20`)"
      - GCC 11
      - Clang 11
      - MSVC 14.27
      - Xcode 13
      - R++

  - desc: "`ranges::elements_view` needs its own sentinel"
    paper: P1994
    lib: true
    support:
      - GCC 10
      - Clang 16
      - Xcode 15
      - MSVC 14.29

  - desc: "Safe integral comparisons"
    paper: P0586
    lib: true
    support:
      - GCC 10
      - Clang 13
      - MSVC 14.27
      - Xcode 13.4.1
    ftm:
      - name: __cpp_lib_integer_comparison_functions
        value: 202002L
    keywords: ["std::cmp_less", "std::cmp_equal", "std::in_range"]

  - desc: "`constexpr` `std::string`"
    paper: [P0426, P1032, P0980]
    lib: true
    support:
      - GCC 12
      - Clang 15
      - MSVC 14.29
      - MSVC 14.30
      - Xcode 14.3
    ftm:
      - name: __cpp_lib_constexpr_string
        value: 201907L

  - desc: "SFINAE-friendly `std::underlying_type`"
    paper: P0340
    summary: "Non-enumeration types have no nested `type`, allowing substitution failure instead of a hard error. Incomplete enumeration types remain ill-formed."
    lib: true
    support: [GCC 9, Clang 9, MSVC 14.25]

  - desc: "Explicit return type for `std::visit<R>()`"
    paper: P0655
    summary: "Convert each visitor result to R, or discard results for void, instead of requiring identical result types."
    lib: true
    support: [GCC 9, Clang 12, MSVC 14.25]

  - desc: "Deprecate POD terminology and `std::is_pod`"
    paper: P0767
    summary: "Use trivial and standard-layout properties separately; `std::is_pod` and `std::is_pod_v` remain available but deprecated."
    lib: true
    support: [GCC 10, Clang 21, MSVC 14.25, Xcode 26.4]

  - desc: "Move `std::endian` to `<bit>` and add its feature-test macro"
    paper: P1612
    lib: true
    support:
      - tool: GCC 9
        status: partial
        note: "Available through `<bit>`, but `__cpp_lib_endian` is missing."
      - GCC 10
      - tool: Clang 9
        status: partial
        note: "Available through `<bit>`, but `__cpp_lib_endian` is missing."
      - Clang 10
      - MSVC 14.25
    ftm:
      - name: __cpp_lib_endian
        value: 201907L

  - desc: "Remove the tuple-like interface of fixed-extent `std::span`"
    paper: P2116
    summary: "Removes span specializations of `std::tuple_size` and `std::tuple_element`, and the `std::get()` overload."
    lib: true
    support: [GCC 10, Clang 11, MSVC 14.27]

  - desc: "`std::ranges::ssize()`"
    paper: P1970
    summary: "Signed size for sized ranges, including ranges sized by subtracting their iterator and sentinel."
    lib: true
    support: [GCC 10, Clang 13]

  - desc: "Revise interruptible `std::condition_variable_any` wait signatures"
    paper: P1869
    summary: "Places `std::stop_token` after the lock argument and renames the untimed `wait_until()` overload to `wait()`."
    lib: true
    support: [GCC 10, Clang 18]
    ftm:
      - name: __cpp_lib_jthread
        value: 201911L

  - desc: "Clarify `std::istream_iterator` initialization and input operations"
    paper: P0738
    summary: "Requires the first read during construction, value-initializes the stored value, and refines constexpr construction and trivial copy/destruction requirements."
    lib: true
    support:
      - GCC 10
      - tool: Clang 15
        status: partial
        note: "Supports construction from `std::default_sentinel`, but the stream constructor does not value-initialize the stored value before the first extraction."
      - MSVC 14.25