C23 (C standard revision)

Changes integrated into the latest working draft of C23 are listed below.{{cite web |title=WG14-N3096: Draft for ISO/IEC 9899:2024 |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20230402172459/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf |archive-date=April 2, 2023 |date=April 1, 2023 |url-status=live}}

• Add memset_explicit() function in <string.h> to erase sensitive data, where memory store must always be performed regardless of optimizations.{{cite web |title=WG14-N2897: memset_explicit() |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2897.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221025074215/https://open-std.org/jtc1/sc22/wg14/www/docs/n2897.htm |archive-date=October 25, 2022 |date=2021-12-27 |url-status=live}}
• Add memccpy() function in to efficiently concatenate strings – similar to POSIX and SVID C extensions.{{cite web |title=WG14-N2349: Toward more efficient string copying and concatenation |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2349.htm |website=open-std.org |archive-url=https://web.archive.org/web/20220930092258/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2349.htm |archive-date=September 30, 2022 |date=2019-03-18 |url-status=live}}
• Add strdup() and strndup() functions in to allocate a copy of a string – similar to POSIX and SVID C extensions.{{cite web |title=WG14-N2353: strdup() and strndup() |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2353.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224063709/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2353.htm |archive-date=December 24, 2022 |date=2019-03-18 |url-status=live}}
• Add memalignment() function in <stdlib.h> to determine the byte alignment of a pointer.{{cite web |title=WG14-N2974: Queryable pointer alignment |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2974.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221013182240/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n2974.pdf |archive-date=October 13, 2022 |date=2022-04-15 |url-status=live}}
• Add bit utility functions / macros / types in new header <stdbit.h> to examine many integer types. All start with stdc_ to minimize conflict with legacy code and 3rd party libraries.{{cite web |title=WG14-N3022: Modern Bit Utilities |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3022.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224194734/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3022.htm |archive-date=December 24, 2022 |date=2022-07-06 |url-status=live}}
• In the following, replace * with uc, us, ui, ul, ull for five function names, or blank for a type-generic macro.
• Add stdc_count_ones*() and stdc_count_zeros*() to count number of 1 or 0 bits in value.
• Add stdc_leading_ones*() and stdc_leading_zeros*() to count leading 1 or 0 bits in value.
• Add stdc_trailing_ones*() and stdc_trailing_zeros*() to count trailing 1 or 0 bits in value.
• Add stdc_first_leading_one*() and stdc_first_leading_zero*() to find first leading bit with 1 or 0 in value.
• Add stdc_first_trailing_one*() and stdc_first_trailing_zero*() to find first trailing bit with 1 or 0 in value.
• Add stdc_has_single_bit*() to determine if value is an exact power of 2 (return true if and only if there is a single 1 bit).
• Add stdc_bit_floor*() to determine the largest integral power of 2 that is not greater than value.
• Add stdc_bit_ceil*() to determine the smallest integral power of 2 that is not less than value.
• Add stdc_bit_width*() to determine number of bits to represent a value.
• Add timegm() function in <time.h> to convert time structure into calendar time value - similar to function in glibc and musl libraries.{{cite web |title=WG14-N2833: Add timegm() as non-optional part of time.h |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2833.htm |website=open-std.org |archive-url=https://web.archive.org/web/20211201062452/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2833.htm |archive-date=December 1, 2021 |date=2021-10-07 |url-status=live}}
• New <math.h> functions based on IEEE 754-2019 recommendations, such as trigonometry functions operating on units of $\backslash pi\; x$ and exp10.See N3096 § B.11 for a useful overview. The functions were added in separate documents: N2488, its updated versions, and its refs.

• Add %b binary conversion specifier to printf() function family.{{cite web |title=WG14-N2630: formatted input/output of binary integer numbers |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2630.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221214154315/https://open-std.org/JTC1/SC22/WG14/www/docs/n2630.pdf |archive-date=December 14, 2022 |date=2021-01-01 |url-status=live}}
• Add %b binary conversion specifier to scanf() function family.
• Add 0b and 0B binary conversion support to strtol() and wcstol() function families.
• Make the functions bsearch(), bsearch_s(), memchr(), strchr(), strpbrk(), strrchr(), strstr(), and their wide counterparts wmemchr(), wcschr(), wcspbrk(), wcsrchr(), wcsstr() return a const qualified object if one was passed to them.{{cite web |title=WG14-N3020: Qualifier-preserving standard library functions |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3020.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221013190826/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n3020.pdf |archive-date=October 13, 2022 |date=2022-06-13 |url-status=live}}

• Add {{C-lang|#elifdef}} and {{C-lang|#elifndef}} directives,{{cite web |title=WG14-N2645: Add support for preprocessing directives #elifdef and #elifndef |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2645.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2645.pdf |archive-date=November 28, 2022 |date=2020-01-25 |url-status=live}} which are essentially equivalent to {{C-lang|#elif defined}} and {{C-lang|#elif !defined}}. Both directives were added to {{nowrap|C++23}} standard and GCC 12.{{cite web |title=GCC 12 Adds Support For New #elifdef #elifndef Directives |url=https://www.phoronix.com/news/GCC-12-elifdef-elifndef |website=phoronix |archive-url=https://web.archive.org/web/20221227050002/https://www.phoronix.com/news/GCC-12-elifdef-elifndef |archive-date=December 27, 2022 |date=May 12, 2021 |url-status=live}}
• Add {{C-lang|#embed}} directive for binary resource inclusion and {{C-lang|__has_embed}} allowing the availability of a resource to be checked by preprocessor directives.{{cite web |title=WG14-N3017: #embed - a scannable, tooling-friendly binary resource inclusion mechanism |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224045304/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm |archive-date=December 24, 2022 |date=2022-06-27 |url-status=live}}
• Add {{C-lang|#warning}} directive for diagnostics.{{cite web |title=WG14-N2686: #warning |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2686.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2686.pdf |archive-date=November 28, 2022 |date=2022-07-22 |url-status=live}}
• Add {{C-lang|__has_include}} allowing the availability of a header to be checked by preprocessor directives.{{cite web |title=WG14-N2799: __has_include for C |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2799.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221224103617/https://open-std.org/JTC1/SC22/WG14/www/docs/n2799.pdf |archive-date=December 24, 2022 |date=2021-08-30 |url-status=live}}
• Add {{C-lang|__has_c_attribute}} allowing the availability of an attribute to be checked by preprocessor directives.{{cite web |title=WG14-N2553: Querying attribute support |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2553.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221014221314/https://open-std.org/JTC1/SC22/WG14/www/docs/n2553.pdf |archive-date=October 14, 2022 |date=2020-08-04 |url-status=live}} (see "{{nowrap|C++}} compatibility" group for new attribute feature)
• Add {{C-lang|__VA_OPT__}} functional macro for variadic macros which expands to its argument only if a variadic argument has been passed to the containing macro.{{cite web |title=WG14-N3033: Comma omission and comma deletion |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3033.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221227031727/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3033.htm |archive-date=December 27, 2022 |date=2022-07-20 |url-status=live}}

• Add nullptr_t, a null pointer type.
• Add {{C-lang|_BitInt(N)}} and {{C-lang|unsigned _BitInt(N)}} types for bit-precise integers. Add {{C-lang|BITINT_MAXWIDTH}} macro for maximum bit width.{{cite web |title=WG14-N2763: Adding a Fundamental Type for N-bit integers |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2763.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221227055250/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2763.pdf |archive-date=December 27, 2022 |date=2021-06-21 |url-status=live}}{{cite web |title=WG14-N3035: _BitInt Fixes |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3035.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221013182206/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n3035.pdf |archive-date=October 13, 2022 |date=2022-07-21 |url-status=live}}
• Add ckd_add(), ckd_sub(), ckd_mul() macros for checked integer operations.{{cite web |title=WG14-N2867: Checked N-Bit Integers |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2867.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221214154907/https://open-std.org/JTC1/SC22/WG14/www/docs/n2867.pdf |archive-date=December 14, 2022 |date=2021-11-28 |url-status=live}}
• Variably-modified types (but not VLAs which are automatic variables allocated on the stack) become a mandatory feature.{{cite web |title=WG14-N2778: Variably-Modified Types |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2778.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221222053411/https://open-std.org/jtc1/sc22/wg14/www/docs/n2778.pdf |archive-date=December 22, 2022 |date=2021-07-11 |url-status=live}}
• Better support for using const with arrays.{{cite web |title=WG14-N2607: Compatibility of Pointers to Arrays with Qualifiers |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2607.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221013182946/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n2607.pdf |archive-date=October 13, 2022 |date=2020-10-31 |url-status=live}}
• Standardization of the typeof(...) operator.{{cite web |title=WG14-N2899: Not-so-magic - typeof for C |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2899.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224044528/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2899.htm |archive-date=December 24, 2022 |date=2022-01-21 |url-status=live}}
• The meaning of the {{C-lang|auto}} keyword was changed to cause type inference while also retaining its old meaning of a storage class specifier if used alongside a type. Unlike C++, C23 allows type inference only for object definitions (no inferring function return type or function parameter type).{{cite web |title=WG14-N3007: Type inference for object definitions |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3007.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224105654/https://open-std.org/JTC1/SC22/WG14/www/docs/n3007.htm |archive-date=December 24, 2022 |date=2022-06-10 |url-status=live}}
• Compatibility rules for structure, union, and enumerated types were changed to allow a redeclaration of a compatible type with the same tag.{{cite web |title=WG14-N3037: Improved Rules for Tag Compatibility (updates N3032) |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3037.pdf}}
• Exact-width integer may now exceed {{code|intmax_t}} (N2888).{{cite web |title=C23 is Finished: Here is What is on the Menu |url=https://thephd.dev/c23-is-coming-here-is-what-is-on-the-menu |website=The Pasture |language=en |date=31 July 2022}}

• Add nullptr constant for nullptr_t type.{{cite web |title=WR14-N3042: Introduce the nullptr constant |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n3042.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224043228/https://open-std.org/JTC1/SC22/WG14/www/docs/n3042.htm |archive-date=December 24, 2022 |date=2022-07-22 |url-status=live}}
• Add wb and uwb integer literal suffixes for {{C-lang|_BitInt(N)}} and {{C-lang|unsigned _BitInt(N)}} types,{{cite web |title=WG14-N2775: Literal suffixes for bit-precise integers |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2775.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221227014728/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2775.pdf |archive-date=December 27, 2022 |date=2021-07-13 |url-status=live}} such as {{C-lang|6uwb}} yields an unsigned _BitInt(3), and {{C-lang|-6wb}} yields a signed _BitInt(4) which has three value bits and one sign bit.
• Add 0b and 0B binary literal constant prefixes,{{cite web |title=WG14-N2549: Allow for binary integer constants |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2549.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221222192818/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2549.pdf |archive-date=December 22, 2022 |date=2020-07-30 |url-status=live}} such as {{C-lang|0b10101010}} (equating to 0xAA).
• Add ' digit separator to literal constants,{{cite web |title=WG14-N2626: Digit separators |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2626.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221219215425/https://open-std.org/JTC1/SC22/WG14/www/docs/n2626.pdf |archive-date=December 19, 2022 |date=2020-12-15 |url-status=live}} such as {{C-lang|0xFE'DC'BA'98}} (equating to 0xFEDCBA98), {{C-lang|299'792'458}} (equating to 299792458), {{C-lang|1.414'213'562}} (equating to 1.414213562).
• Add the ability to specify the underlying type of an enum.{{cite web |title=WG14-N3030: Enhancements to Enumerations |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n3030.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221126132709/https://open-std.org/JTC1/SC22/WG14/www/docs/n3030.htm |archive-date=November 26, 2022 |date=2022-07-19 |url-status=live}}
• Allow {{C-lang|enum}}s with no fixed underlying type to store values that are not representable by {{C-lang|int}}.{{cite web |title=WG14-N3029: Improved Normal Enumerations |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n3029.htm |website=open-std.org |archive-url=https://web.archive.org/web/20230129180341/https://open-std.org/JTC1/SC22/WG14/www/docs/n3029.htm |archive-date=January 29, 2023 |date=2022-07-19 |url-status=live}}

• Add {{C-lang|true}} and {{C-lang|false}} keywords.{{cite web |title=WG14-N2935: Make false and true first-class language features |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2935.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221121123457/https://open-std.org/JTC1/SC22/WG14/www/docs/n2935.pdf |archive-date=November 21, 2022 |date=2022-02-15 |url-status=live}}
• Add {{C-lang|alignas}}, {{C-lang|alignof}}, {{C-lang|bool}}, {{C-lang|static_assert}}, thread-local storage keywords. Previously defined keywords become alternative spellings: {{C-lang|_Alignas}}, {{C-lang|_Alignof}}, {{C-lang|_Bool}}, {{C-lang|_Static_assert}}, {{C-lang|_Thread_local}}.{{cite web |title=WG14-N2934: Revise spelling of keywords |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2934.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221224132455/https://open-std.org/JTC1/SC22/WG14/www/docs/n2934.pdf |archive-date=December 24, 2022 |date=2022-02-15 |url-status=live}}
• Add {{C-lang|_BitInt}} keyword (see "types" group)
• Add {{C-lang|typeof}} and {{C-lang|typeof_unqual}} keywords (see "types" group)
• Add {{C-lang|nullptr}} keyword (see "constants" group)
• Add {{C-lang|constexpr}} keyword (see "other" group)
• Add {{C-lang|_Decimal32}}, {{C-lang|_Decimal64}}, {{C-lang|_Decimal128}} keywords for (optional) decimal floating-point arithmetic (see "other" group)

• Labels can appear before declarations and at the end of compound statements.{{cite web |title=WG14-N2508: Free Positioning of Labels Inside Compound Statements |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2508.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221227183107/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2508.pdf |archive-date=December 27, 2022 |date=2020-03-28 |url-status=live}}
• Unnamed parameters in function definitions.{{cite web |title=WG14-N2510: Allowing unnamed parameters in a function definition |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2510.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221224075948/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2510.pdf |archive-date=December 24, 2022 |date=2020-04-09 |url-status=live}}
• Zero initialization with {} (including initialization of VLAs).{{cite web |title=WG14-N2900: Consistent, Warningless, and Intuitive Initialization with {} |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2900.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221227181452/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2900.htm |archive-date=December 27, 2022 |date=2022-01-01 |url-status=live}}
• Variadic functions no longer need a named argument before the ellipsis and the {{C-lang|va_start}} macro no longer needs a second argument nor does it evaluate any argument after the first one if present.{{cite web |title=WG14-N2975: Relax requirements for variadic parameter lists |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2975.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2975.pdf |archive-date=November 28, 2022 |date=2022-04-15 |url-status=live}}
• Add C++11 style attribute syntax{{cite web |title=WG14-N2335: Attributes in C |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2335.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221026060722/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2335.pdf |archive-date=October 26, 2022 |date=2019-03-09 |url-status=live}} using double square brackets {{C-lang|1=}}. In addition to C++11 attributes listed below, add new attributes:
• unsequenced{{Cite web |title=Unsequenced functions |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n2956.htm |access-date=2024-07-18 |website=open-std.org}} allows compiler optimizations for functions producing repeatable outputs only based on their parameters
• reproducible, similar to unsequenced, but for functions whose call order also matters
• Add single-argument _Static_assert for compatibility with C++17.{{cite web |title=WG14-N2265: Harmonizing static_assert with C++ |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n2265.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20230328064918/https://open-std.org/JTC1/SC22/WG14/www/docs/n2265.pdf |archive-date=March 28, 2023 |date=2018-07-06 |url-status=live}}
• Functions with no arguments listed in the prototype (e.g. void foo()) are understood as taking no arguments (see removal of K&R function declarations)

• Various syntax changes improve compatibility with C++, such as labels before declarations, unnamed function arguments, zero initialization with {}, variadic functions without named argument, C++11 style attributes, _Static_assert (see Syntax). For labels at the end of compound statements a corresponding change was made to C++23.{{cite web|url=https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2324r2.pdf|title=Labels at the end of compound statements (C compatibility)|date=2022-01-13}}
• Add C++-style attributes (see Syntax). Add attributes{{cite web |title=WG14-N2554: Minor attribute wording cleanups |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2554.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2554.pdf |archive-date=November 28, 2022 |date=2020-08-04 |url-status=live}} {{C-lang|1=deprecated}},{{cite web |title=WG14-N2334: The deprecated attribute |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2334.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221019131835/https://open-std.org/JTC1/SC22/WG14/www/docs/n2334.pdf |archive-date=October 19, 2022 |date=2019-01-22 |url-status=live}} {{C-lang|1=fallthrough}},{{cite web |title=WG14-N2408: The fallthrough attribute |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2408.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221225070709/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2408.pdf |archive-date=December 25, 2022 |date=2019-08-11 |url-status=live}} {{C-lang|1=maybe_unused}},{{cite web |title=WG14-N2270: The maybe_unused attribute |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2270.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221225070836/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2270.pdf |archive-date=December 25, 2022 |date=2018-07-06 |url-status=live}} {{C-lang|1=nodiscard}},{{cite web |title=WG14-N2267: The nodiscard attribute |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2267.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221019131846/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2267.pdf |archive-date=October 19, 2022 |date=2018-07-06 |url-status=live}} and {{C-lang|1=noreturn}} attribute for compatibility with C++11, then deprecate {{C-lang|_Noreturn}}, {{C-lang|noreturn}}, header features introduced in C11.{{cite web |title=WG14-N2764: The noreturn attribute |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n2764.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221225063437/https://open-std.org/JTC1/SC22/WG14/www/docs/n2764.pdf |archive-date=December 25, 2022 |date=2021-06-21 |url-status=live}} Duplicate attributes are allowed for compatibility with C++23.{{cite web |title=WG14-N2557: Allow Duplicate Attributes |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2557.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2557.pdf |archive-date=November 28, 2022 |date=2020-09-01 |url-status=live}} All standard attributes can also be surrounded by double underscores (e.g. {{C-lang|1=__deprecated__}} is equivalent to {{C-lang|1=deprecated}}).
• Add u8 prefix for character literals to represent UTF-8 encoding for compatibility with C++17.{{cite web |title=WG14-N2418: Adding the u8 character prefix |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2418.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20230113210023/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2418.pdf |archive-date=January 13, 2023 |date=2019-09-02 |url-status=live}}[https://stackoverflow.com/questions/31970111/what-is-the-point-of-the-utf-8-character-literals-proposed-for-c17#31970297 What is the point of the UTF-8 character literals proposed for C++17?; Stack Overflow.]
• Add {{C-lang|#elifdef}} and {{C-lang|#elifndef}} preprocessing directives for compatibility with C++23. (see "preprocessor" group)

• Support for the ISO/IEC 60559:2020, the current version of the IEEE 754 standard for floating-point arithmetic, with extended binary floating-point arithmetic and (optional) decimal floating-point arithmetic.{{cite web |title=WG14-N2341: ISO/IEC TS 18661-2 - Floating-point extensions for C - Part 2: Decimal floating-point arithmetic |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2341.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221121122559/https://open-std.org/JTC1/SC22/WG14/www/docs/n2341.pdf |archive-date=November 21, 2022 |date=February 26, 2019 |url-status=live}}{{cite web |title=WG14-N2601: Annex X - IEC 60559 interchange and extended types |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2601.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221014221322/https://open-std.org/JTC1/SC22/WG14/www/docs/n2601.pdf |archive-date=October 14, 2022 |date=October 15, 2020 |url-status=live}}

• The constexpr specifier for objects but not functions, unlike C++'s equivalent.{{cite web |title=WG14-N3018: The constexpr specifier for object definitions |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3018.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221224074302/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3018.htm |archive-date=December 24, 2022 |date=2022-07-06 |url-status=live}}
• Add {{C-lang|char8_t}} type for storing UTF-8 encoded data and change the type of u8 character constants and string literals to {{C-lang|char8_t}}. Also, the functions mbrtoc8() and c8rtomb() to convert a narrow multibyte character to UTF-8 encoding and a single code point from UTF-8 to a narrow multibyte character representation respectively.{{cite web |title=WG14-N2653: char8_t: A type for UTF-8 characters and strings (Revision 1) |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2653.htm |website=open-std.org |archive-url=https://web.archive.org/web/20230527110842/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2653.htm |archive-date=May 27, 2023 |date=2021-06-04 |url-status=live}}
• Clarify that all {{C-lang|char16_t}} strings and literals shall be UTF-16 encoded, and all {{C-lang|char32_t}} strings and literals shall be UTF-32 encoded, unless otherwise explicitly specified.{{cite web |title=WG14-N2728: char16_t & char32_t string literals shall be UTF-16 & UTF-32 |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2728.htm |website=open-std.org |archive-url=https://web.archive.org/web/20230527110756/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2728.htm |archive-date=May 27, 2023 |date=2021-05-15 |url-status=live}}
• Allow storage class specifiers to appear in compound literal definition.{{cite web |title=WG14-N3038: Introduce storage-class specifiers for compound literals |url=https://open-std.org/JTC1/SC22/WG14/www/docs/n3038.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221126130057/https://open-std.org/JTC1/SC22/WG14/www/docs/n3038.htm |archive-date=November 26, 2022 |date=2022-07-21 |url-status=live}}

Some old obsolete features are either removed or deprecated from the working draft of C23:

:* Remove trigraphs.{{cite web |title=WG14-N2940: Removing trigraphs??! |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2940.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221026005747/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2940.pdf |archive-date=October 26, 2022 |date=2022-03-02 |url-status=live}}

:* Remove K&R function definitions/declarations (with no information about the function arguments).{{cite web |title=WG14-N2432: Remove support for function definitions with identifier lists proposal |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2432.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221227012244/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2432.pdf |archive-date=December 27, 2022 |date=September 25, 2019 |url-status=live}}{{cite web |title=WG14-N2841: No function declarators without prototypes |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2841.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221112154740/https://www9.open-std.org/jtc1/sc22/wg14/www/docs/n2841.htm |archive-date=November 12, 2022 |date=2021-10-10 |url-status=live}}

:* Remove representations for signed integers other than two's complement. Two's complement signed integer representation will be required.{{cite web |title=WG14-N2412: Two's complement sign representation |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2412.pdf |website=open-std.org |archive-url=https://web.archive.org/web/20221227174224/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2412.pdf |archive-date=December 27, 2022 |date=August 11, 2019 |url-status=live}}

:* The {{C-lang|*_HAS_SUBNORM}} macros in are obsolescent features.{{cite web |title=WG14-N2993: Make *_HAS_SUBNORM be obsolescent |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2993.htm |website=open-std.org |archive-url=https://web.archive.org/web/20221205194635/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2993.htm |archive-date=December 5, 2022 |date=2022-06-06 |url-status=live}}

The following compilers implement an experimental compiler flag to support this standard:

• GCC 9,{{cite web |title=GCC 9 Release Notes |url=https://gcc.gnu.org/gcc-9/changes.html#c |url-status=live |archive-url=https://web.archive.org/web/20221227032646/https://gcc.gnu.org/gcc-9/changes.html |archive-date=December 27, 2022 |website=GNU Project}}
• Clang 9.0,{{cite web |date=May 14, 2019 |title=Clang 9.0 - add new language mode for C2x |url=https://github.com/llvm/llvm-project/commit/d06f3917913d2558b771ccc48d838f8cd8993c01 |url-status=live |archive-url=https://web.archive.org/web/20221227032640/https://github.com/llvm/llvm-project/commit/d06f3917913d2558b771ccc48d838f8cd8993c01 |archive-date=December 27, 2022 |website=LLVM Project Repository}}
• Pelles C 11.00{{cite web |title=Pelles C - major changes between 10.00 and 11.00 |url=http://www.smorgasbordet.com/pellesc/changes_1000_1100.htm |url-status=live |archive-url=https://web.archive.org/web/20221227032644/http://www.smorgasbordet.com/pellesc/changes_1000_1100.htm |archive-date=December 27, 2022 |website=smorgasbordet.com}}

Like other editions of the C standard, the official ISO text of the standard is not freely available.

The latest working draft pre-C23 that was made public was N3096, dated 2023-04-01. In the months that followed this draft, hundreds of changes{{cite web |title=N3150 - Editor's Report, Post January-February 2023 Meeting |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3150.htm |website=open-std.org |date=2023-07-08}} were made before producing the working draft N3149 dated 2023-07-09 and the official draft standard N3219 dated 2024-02-22.{{cite web |title=N3221 - Editor's Report, Post January 2024 Meeting |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3221.htm |website=open-std.org |date=2024-02-15}} Neither of these later drafts are public.

On the same date that the draft standard N3219 was announced, a new working draft N3220{{cite web |title=ISO/IEC 9899:2024 (en) — N3220 working draft |url=https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf |website=open-std.org |date=2024-02-22}} was made public. While this document is officially described as a draft of the future version "C2Y" of the standard, the accompanying "Editor's Report" specifies that N3220 differs from the draft C23 standard N3219 only by a fix to one footnote in Annex K.

{{Portal|Computer programming}}

• C++23, C++20, C++17, C++14, C++11, C++03, C++98, versions of the C++ programming language standard
• Compatibility of C and C++

{{Reflist}}

• [https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf N3096] (last freely-available working draft before C23); WG14; April 2023. (free download)
• N3149 (working draft of C23 standard); WG14; July 2023. (not available to public)
• N3219 ([https://www.iso.org/standard/82075.html ISO/IEC 9899:2023 DIS Draft]); WG14; February 2024. (ISO draft available but not free)
• ISO/IEC 9899:2024 (official C23 standard); ISO; 2024. (planning for release in 2024)
• [https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf N3220] (first working draft after C23; differs from draft standard N3219 only in one footnote); WG14; February 2024. (free download)

• [https://www.open-std.org/jtc1/sc22/wg14/ C Language WG14 (Working Group 14)]

:* [https://www.open-std.org/jtc1/sc22/wg14/www/wg14_document_log.htm WG14 Document Repository]

:* [https://www.open-std.org/jtc1/sc22/wg14/www/meetings WG14 Meetings] - agenda and minutes

:* WG14 Charters: [https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2021.htm C2x Charter], [https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2611.htm C23 Charter], [https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2986.htm Interpreting the C23 Charter], [https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3223.pdf C Standard Charter]

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Category:C (programming language)

Category:Programming language standards