C23

 

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Strings library

Algorithms

Numerics

Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Symbol index

 

Versions

C89

C95

C99

C11

C17

C23

Current Status

 

The next generation of the C standard.

See: The current IS schedule for C23.

Obsolete

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

Deprecated

• Old feature-test macros
  • __STDC_IEC_559__
  • __STDC_IEC_559_COMPLEX__
• DECIMAL_DIG
• Definition of following numeric limit macros in <math.h> (they should be used via <limits.h>)
  • INFINITY
  • DEC_INFINITY
  • NAN
  • DEC_NAN
• _Noreturn function specifier
• _Noreturn attribute token
• __bool_true_false_are_defined

New language features

• Decimal floating-point types (_Decimal32, _Decimal64, and _Decimal128)
• Binary integer constants
• u8 character constants
• Type change of u8 string literals
• Digit separator '
• Empty initializer = {}
• Attributes
  • [[deprecated]]
  • [[fallthrough]]
  • [[maybe_unused]]
  • [[nodiscard]]
  • [[noreturn]]
• Unnamed parameters in function definitions
• Identical cvr-qualifications for array types and their element types
• Single-argument _Static_assert
• Labels followed by declarations and }
• New preprocessor directives
  • #elifdef
  • #elifndef
  • #warning
• Pragmas for rounding direction
  • STDC FENV_ROUND
  • STDC FENV_DEC_ROUND

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__.

New library features

• Extended binary floating-point math functions
• 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
• POSIX functions
  • memccpy()
  • strdup()
  • strndup()
  • asctime_r()
  • ctime_r()
  • gmtime_r()
  • localtime_r()
  • Extensions for strftime() and wcsftime()
• Extensions for fscanf() and fprintf() function families
  • wN and wfN length modifiers for [u]intN_t and [u]int_fastN_t respectively
  • H, D, and DD 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
  • __STDC_VERSION_FENV_H__
  • __STDC_VERSION_MATH_H__
  • __STDC_VERSION_STDINT_H__
  • __STDC_VERSION_STDLIB_H__
  • __STDC_VERSION_TGMATH_H__
  • __STDC_VERSION_TIME_H__

Defect reports

Defect Reports fixed in C23 (? defects)
DR 440 DR 432 DR 467 DR 476 DR 482 DR 488 DR 489 DR 494 DR 496 DR 497 DR 499 DR 500 DR 501

Compiler support

C23 core language features

C23 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	IBM XLC++	Sun/Oracle C++	Embarcadero C++ Builder	Cray	Nvidia HPC C++ (ex Portland Group/PGI)	Nvidia nvcc
_Static_assert with no message	N2265	9	9		Yes
[[nodiscard]]	N2267	10	9		Yes
[[maybe_unused]]	N2270	10	9		Yes
[[deprecated]]	N2334	10	9		Yes
Attributes	N2335 N2554	10	9		Yes
IEEE 754 decimal floating-point types	N2341	4.2 (partial)*					13.0 (partial)*
[[fallthrough]]	N2408	10	9		Yes
u8 character constants	N2418	10	15
Removal of function definitions without prototype	N2432	10	15
[[nodiscard]] with message	N2448	11	10		Yes
Unnamed parameters in function definitions	N2480	11	11		Yes
Labels before declarations and end of blocks	N2508	11		Partial*			17.0*
Binary integer constants	N2549	4.3* 11	2.9* 9	19.0 (2015)**	Yes		11.0*
__has_c_attribute in preprocessor conditionals	N2553	11	9		Yes
Allow duplicate attributes	N2557	11	13		Yes
IEEE 754 interchange and extended types	N2601	7 (partial)*	6 (partial)*		Partial*
Digit separators	N2626	12	13	19.0 (2015)**	Yes		18.0*
#elifdef and #elifndef	N2645	12	13		13.1.6*
Type change of u8 string literals	N2653
[[maybe_unused]] for labels	N2662	11
#warning	N2686	Yes	Yes		Yes	Yes	Yes
Bit-precise integer types (_BitInt)	N2763		15
[[noreturn]]	N2764		15
Suffixes for bit-precise integer constants	N2775		15
__has_include in preprocessor conditionals	N2799	5	Yes	19.11*	Yes	4.13	18.0
Removal of function declarations without prototype	N2841		15
Empty initializers	N2900	Partial*	Partial*		Partial*	Partial*	Partial*
typeof and remove_quals	N2927	Partial*	Partial*		Partial*	Partial*	Partial*				Partial*
C23 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	IBM XLC++	Sun/Oracle C++	Embarcadero C++ Builder	Cray	Nvidia HPC C++	Nvidia nvcc