C23
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ISO/IEC 9899:2024, a.k.a. C23 is the current revision of the C standard.
- The latest publicly available WD of C23 (n3301, 2024-07-28).
- The latest WD of C23 (n3149, 2023-07-09, a password-protected zip archive, see n3150).
This section is incomplete Reason: accepted changes not yet included in the working draft |
Contents |
[edit] Obsolete
[edit] Removed
- Old-style function declarations and definitions
- Representations for signed integers other than two's complement
- Permission that u/U-prefixed character constants and string literals may be not UTF-16/32
- Mixed wide string literal concatenation
- Support for calling realloc() with zero size (the behavior becomes undefined)
- __alignof_is_defined and __alignas_is_defined
- static_assert is not provided as a macro defined in <assert.h> (becomes a keyword)
- thread_local is not provided as a macro defined in <threads.h> (becomes a keyword)
[edit] Deprecated
- <stdnoreturn.h>
- Old feature-test macros
- _Noreturn function specifier
- _Noreturn attribute token
- asctime()
- ctime()
- DECIMAL_DIG (use the appropriate type-specific macro (FLT_DECIMAL_DIG, etc) instead)
- Definition of following numeric limit macros in <math.h> (they should be used via <float.h>)
- __bool_true_false_are_defined
[edit] New language features
- Decimal floating-point types (_Decimal32, _Decimal64, and _Decimal128)
- Bit-precise integers (_BitInt)
- Binary integer constants
-
u8
character constants - Type change of
u8
string literals - Digit separator
'
- Empty initializer ={}
- Attributes
-
[[deprecated]]
-
[[fallthrough]]
-
[[maybe_unused]]
-
[[nodiscard]]
-
[[noreturn]]
-
[[reproducible]]
-
[[unsequenced]]
-
- Unnamed parameters in function definitions
- Identical cvr-qualifications for array types and their element types
- Single-argument _Static_assert
- static_assert becomes a keyword (may be a predefined macro for compatibility reasons)
- thread_local becomes a keyword (may be a predefined macro for compatibility reasons)
- Labels followed by declarations and
}
- nullptr constant and the associated nullptr_t type
- true and false become keywords (may be predefined macros for compatibility reasons)
- New preprocessor directives
- Pragmas for rounding direction
-
STDC
FENV_ROUND -
STDC
FENV_DEC_ROUND
-
[edit] Feature test macros for optional features
- __STDC_IEC_60559_BFP__
- Indicates IEEE-754 binary floating-point arithmetic and required math functions are supported.
- This macro supersedes __STDC_IEC_559__.
- __STDC_IEC_60559_DFP__
- Indicates IEEE-754 decimal floating-point arithmetic and required math functions are supported.
- __STDC_IEC_60559_COMPLEX__
- Indicates IEEE-754 complex arithmetic and required math functions are supported.
- This macro supersedes __STDC_IEC_559_COMPLEX__.
[edit] New library features
[edit] New headers
- <stdbit.h>
- <stdckdint.h>
[edit] Library features
- Extended binary floating-point math functions
-
This section is incomplete
Reason: List TBD
-
- Decimal floating-point math functions
- -
dN
variants for existing and new floating-point math functions - quantizedN()
- samequantumdN()
- quantumdN()
- llquantexpdN()
- encodedecdN()
- decodedecdN()
- encodebindN()
- decodebindN()
- -
- Floating-point formatting functions
- Library support for UTF-8
-
char8_t
type alias - mbrtoc8()
- c8rtomb()
- atomic_char8_t type alias
- ATOMIC_CHAR8_T_LOCK_FREE test macro
-
- memset_explicit()
- POSIX functions
- memccpy()
- strdup()
- strndup()
- gmtime_r()
- localtime_r()
- Extensions for strftime() and wcsftime()
- Extensions for fscanf() and fprintf() function families
-
wN
andwfN
length modifiers for [u]intN_t and [u]int_fastN_t respectively -
H
,D
, andDD
length modifiers for _Decimal32, _Decimal64, and _Decimal128 respectively -
b
conversion specifier for unsigned integer types
-
- timespec_getres()
- Macro constants for width of integer types
- Additional numeric limit macros for floating-point types
- Library version-test macros
[edit] Defect reports
Defect Reports fixed in C23 (? defects) |
---|
[edit] Compiler support
[edit] C23 core language features
This section is incomplete Reason: status for Apple Clang and other compilers supporting C2x |
C23 feature |
Paper(s) |
GCC |
Clang |
MSVC |
Apple Clang |
EDG eccp |
Intel C++ |
Nvidia HPC C++ (ex PGI)* |
Nvidia nvcc |
Cray |
|||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
_Static_assert with no message | N2265 | 9 | 9 | Yes | Yes | 6.5 | 2021.1.2 (clang based) | ||||||||||
[[nodiscard]]
|
N2267 | 10 | 9 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
[[maybe_unused]]
|
N2270 | 10 | 9 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
[[deprecated]]
|
N2334 | 10 | 9 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
Attributes | N2335 N2554 |
10 | 9 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
IEEE 754 decimal floating-point types | N2341 | 4.2 (partial)* 12 |
13.0 (partial)* | ||||||||||||||
[[fallthrough]]
|
N2408 | 10 | 9 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
u8 character constants
|
N2418 | 10 | 15 | 6.5 | 2022.2 | ||||||||||||
Removal of function definitions without prototype | N2432 | 10 | 15 | 2022.2 | |||||||||||||
[[nodiscard]] with message
|
N2448 | 11 | 10 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
Unnamed parameters in function definitions | N2480 | 11 | 11 | Yes | 6.4 | 2021.1.2 (clang based) | |||||||||||
Labels before declarations and end of blocks | N2508 | 11 | 16 | Partial* | 6.5 | 17.0* | |||||||||||
Binary integer constants | N2549 | 4.3* 11 |
2.9* 9 |
19.0 (2015)** | Yes | 6.5 | 11.0* | ||||||||||
__has_c_attribute in preprocessor conditionals | N2553 | 11 | 9 | Yes | 6.5 | 2021.1.2 (clang based) | |||||||||||
Allow duplicate attributes | N2557 | 11 | 13 | Yes | 6.5 | 2021.4 (clang-based | |||||||||||
IEEE 754 interchange and extended types | N2601 | 7 (partial)* 14 |
6 (partial)* | Partial* | |||||||||||||
Digit separators | N2626 | 12 | 13 | 19.0 (2015)** | Yes | 6.5 | 18.0* | ||||||||||
#elifdef and #elifndef
|
N2645 | 12 | 13 | 19.40* | 13.1.6* | 6.5 | 2021.4 | ||||||||||
Type change of u8 string literals
|
N2653 | 13 | |||||||||||||||
[[maybe_unused]] for labels
|
N2662 | 11 | 16 | 6.5 | 2022.2 | ||||||||||||
#warning | N2686 | Yes | Yes | Yes | 6.5 | Yes | |||||||||||
Bit-precise integer types (_BitInt) | N2763 | 14 (partial)* | 15 | 6.5 | 2022.2 | ||||||||||||
[[noreturn]]
|
N2764 | 13 | 15 | 6.5 | 2022.2 | ||||||||||||
Suffixes for bit-precise integer constants | N2775 | 14 | 15 | 2022.2 | |||||||||||||
__has_include in preprocessor conditionals | N2799 | 5 | Yes | 19.11* | Yes | 6.5 | 18.0 | ||||||||||
Identifier Syntax using Unicode Standard Annex 31 | N2836 | 13 | 15 | 6.5 | 2022.2 | ||||||||||||
Removal of function declarations without prototype | N2841 | 13 | 15 | 2022.2 | |||||||||||||
Empty initializers | N2900 | Partial* 13 |
Partial* | Partial* | Partial* | Partial* | |||||||||||
typeof and typeof_unqual | N2927 N2930 |
Partial* 13 |
Partial* 16 |
19.39* | Partial* | Partial* | Partial* | Partial* | |||||||||
New spelling of keywords | N2934 | 13 | 16 | 6.5 | |||||||||||||
Predefined true and false
|
N2935 | 13 | 15 | 2022.2 | |||||||||||||
[[unsequenced]] and [[reproducible]]
|
N2956 | 15 | |||||||||||||||
Relax requirements for variadic parameter list | N2975 | 13 | 16 | 6.5 | 2023.1 | ||||||||||||
Type inference in object definitions | N3007 | 13 | 18 | ||||||||||||||
#embed | N3017 | 15 | 19 | ||||||||||||||
constexpr objects | N3018 | 13 | 19 | ||||||||||||||
Improved Normal Enumerations | N3029 | 13 | 20* | ||||||||||||||
Enumerations with fixed underlying types | N3030 | 13 | 20* | ||||||||||||||
__VA_OPT__
|
N3033 | 8 13 |
12 | 19.39* | 6.5 | ||||||||||||
Storage-class specifiers for compound literals | N3038 | 13 | |||||||||||||||
nullptr | N3042 | 13 | 16 | ||||||||||||||
C23 feature |
Paper(s) |
GCC |
Clang |
MSVC |
Apple Clang |
EDG eccp |
Intel C++ |
Nvidia HPC C++ (ex PGI)* |
Nvidia nvcc |
Cray |
[edit] C23 library features
This section is incomplete Reason: a different list for C standard libraries |