features_c2y.yaml

---
features:
  - desc: "Round-trip rounding"
    paper: N3232
    lib: true
    support:
      - GCC ?
      - Clang

  - desc: "Slay Some Earthly Demons I"
    paper: N3244
    support:
      - GCC ?
      - Clang (partial)
      - Xcode 16.3 (partial)
    hints:
      - target: Clang
        msg: "Clang does not document the implementation-defined behavior for decay of an array with the register storage class specifier. Clang does not diagnose an extern inline function with no definition in the TU. Clang accepts and rejects redeclarations with/without an alignment specifier, depending on the order of the declarations."
      - target: Xcode 16.3
        msg: "See hint for Clang."

  - desc: "Accessing byte arrays"
    paper: N3254
    support:
      - GCC 15
      - Clang 18
      - Xcode 16.4

  - desc: "Support `++` and `--` on complex values"
    paper: N3259
    content: c-complex-inc-dec.md
    support:
      - GCC 3
      - Clang 18
      - Xcode 16.4

  - desc: "Generic selection expression with a type operand"
    paper: N3260
    content: c-generic-type-operand.md
    support:
      - GCC 15
      - Clang 17
      - Xcode 16.4

  - desc: "`alignof` of an incomplete array type"
    paper: N3273
    content: c-alignof-incomplete.md
    support:
      - GCC 15
      - Clang 3.5

  - desc: "Remove imaginary types"
    paper: N3274
    support:
      - GCC (hint)
      - Clang (hint)
      - Xcode (hint)
    hints:
      - target: GCC
        msg: "GCC has never supported imaginary types."
      - target: Clang
        msg: "Clang has never supported imaginary types."
      - target: Xcode
        msg: "Apple Clang has never supported imaginary types."

  - desc: "Floating-point exceptions for macro replacements"
    paper: N3286
    lib: true
    support:
      - Clang
      - Xcode 16.4

  - desc: "Introduce complex literals"
    paper: N3298
    content: c-complex-literals.md
    support:
      - GCC 2.5
      - Clang
      - Xcode 16.4

  - desc: "Allowing stricter alignment for atomic types"
    paper: N3312
    support:
      - Clang
      - Xcode 16.4

  - desc: "Allow zero length operations on null pointers"
    paper: N3322
    support:
      - GCC 15
      - Clang
      - Xcode 16.4

  - desc: "How do you add one to something?"
    paper: N3323
    support:
      - Clang
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons III"
    paper: N3341
    support:
      - Clang
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons IV"
    paper: N3342
    support:
      - Clang
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons VI"
    paper: N3344
    support:
      - Clang 20
      - GCC
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons VII"
    paper: N3345
    support:
      - Clang
      - GCC
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons VIII"
    paper: N3346
    support:
      - Clang
      - GCC
      - Xcode 16.3

  - desc: "Slay Some Earthly Demons IX"
    paper: N3347
    support:
      - Clang
      - GCC
      - Xcode 16.4

  - desc: "Matching of Multi-Dimensional Arrays in Generic Selection Expressions"
    paper: N3348
    support:
      - GCC 16

  - desc: "Obsolete implicitly octal literals and delimited escape sequences"
    paper: N3353
    content: c-octal-literals.md
    support:
      - GCC 15
      - Clang 21
      - Xcode 26.4

  - desc: "Named loops"
    paper: N3355
    content: c-named-loops.md
    support:
      - GCC 15
      - Clang 22

  - desc: "`if` declarations"
    paper: N3356
    content: c-if-declarations.md
    support:
      - GCC 15

  - desc: "Consistent wording for SNAN initialization"
    paper: N3364
    support:
      - Clang
      - Xcode 16.4

  - desc: "Case range expressions (`case x ... y`)"
    paper: N3370
    content: c-case-range.md
    support:
      - GCC 2
      - Clang
      - Xcode 16.4

  - desc: "`stdarg.h` wording improvements"
    paper: N3363
    support:
      - Clang 5
      - Xcode 16.4

  - desc: "`_Countof` operator"
    paper:
      - N3369
      - N3469
    content: c-countof.md
    support:
      - GCC 16
      - Clang 21
      - Xcode 26.4

  - desc: "Restartable Functions for Efficient Character Conversions"
    paper: N3366
    support:
      - Clang ?
      - MSVC ?

  - desc: "Abs Without Undefined Behavior"
    paper: N3349
    support:
      - Clang ?
      - MSVC ?

  - desc: "More Modern Bit Utilities"
    paper: N3367
    support:
      - Clang ?
      - MSVC ?

  - desc: "Error conditions in `<math.h>`"
    paper: N3405
    lib: true

  - desc: "Slay Some Earthly Demons X"
    paper: N3409
    support:
      - Clang 21
      - Xcode 26.4

  - desc: "Slay Some Earthly Demons XI"
    paper: N3410
    support:
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons XII"
    paper: N3411
    support:
      - Clang 21
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons XIV"
    paper: N3418

  - desc: "Anonymous structure/union initialization"
    paper: N3451
    support:
      - Clang

  - desc: "The `__COUNTER__` predefined macro"
    paper: N3457
    content: c-counter-macro.md
    support:
      - Clang 22
      - Xcode 16.3 (hint)
    hints:
      - target: Xcode 16.3
        msg: "Supported as a pre-existing GNU extension prior to C2y standardization."

  - desc: "Complex operators"
    paper: N3460
    support:
      - Clang 12
      - Xcode 16.4

  - desc: "Range error definition followup"
    paper: N3461
    lib: true

  - desc: "Preprocessor integer expressions"
    paper:
      - N3465
      - N3505
    support:
      - Clang

  - desc: "Null pointer clarifications in library"
    paper: N3466
    lib: true
    support:
      - GCC 16
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons XIII"
    paper: N3478
    support:
      - GCC
      - Clang

  - desc: "Slay Some Earthly Demons XVI"
    paper: N3481
    support:
      - GCC
      - Clang
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons XVII"
    paper: N3482
    support:
      - GCC
      - Clang
      - Xcode 16.4

  - desc: "Slay Some Earthly Demons V"
    paper: N3484
    support:
      - GCC
      - Clang
      - Xcode 16.4

  - desc: "Error conditions for narrow type rounding"
    paper: N3492
    lib: true

  - desc: "Clarify width macros specification"
    paper: N3496
    support:
      - Clang 20
      - Xcode 16.4

  - desc: "`static_assert` without UB"
    paper: N3525
    support:
      - Clang
      - Xcode 16.3

  - desc: "Member access of an incomplete object"
    paper: N3532
    support:
      - GCC
      - MSVC
      - Clang
      - Xcode

  - desc: "Chasing Ghosts I: constant expressions"
    paper: N3558
    support:
      - GCC ?
      - MSVC ?
      - Clang ?
      - Xcode ?

  - desc: "Generic replacement (quasi-literals)"
    paper: N3605
    support:
      - Clang
      - Xcode 26.4

  - desc: "Allow calling `static inline` within `extern inline`"
    paper: N3622
    support:
      - GCC (partial)
      - Clang 22
      - Xcode 16.3 (partial)
    hints:
      - target: Xcode 16.3
        msg: "Code compiles but emits `-Wstatic-in-inline` warning. Full C2y semantics (warning suppression in `c2y` mode) require Clang 22."
      - target: GCC
        msg: "Code compiles but emits a warning."

  - desc: "Earthly Demon XV: Definition of Main"
    paper: N3623
    support:
      - GCC
      - Clang
      - Xcode 16.3

  - desc: "Composite types"
    paper: N3652
    support:
      - GCC 16 (partial)

  - desc: "static_assert expressions"
    paper: N3715

  - desc: "Earthly Demon: Accessing a Member of an Atomic Structure or Union"
    paper: N3653
    support:
      - GCC
      - Clang

  - desc: "Const integer declarations as implicit named constants"
    paper: N3833
    content: c-const-constexpr.md
    support:
      - GCC (partial)
      - Clang (partial)
      - Xcode 16.3 (partial)
    hints:
      - target: Xcode 16.3
        msg: "Constant folding of const integers works via a GNU extension, not native C2y constexpr semantics. Issues a `-Wgnu-folding-constant` warning under `-pedantic`."

  - desc: "Enumerations with Bit-Precise Integer as Underlying Type"
    paper: N3705

  - desc: "The Elvis operator ?:"
    paper: N3804
    support:
      - GCC
      - Clang