C23 (C standard revision) explained

C23 is the informal name for ISO/IEC 9899:2024, the next standard for the C programming language, which will replace C17 (standard ISO/IEC 9899:2018).^[1] It was started in 2016 informally as C2x,^[2] and is expected to be published in 2024.^[3] The most recent publicly available working draft of C23 was released on April 1, 2023. The first WG14 meeting for the C2x draft was held in October 2019,^[4] virtual remote meetings were held in 2020 due to the COVID-19 pandemic, then various teleconference meetings continued to occur through 2024.

Features

Changes integrated into the latest working draft of C23 are listed below.^[5]

Standard Library

New functions

• Add memset_explicit function in <[[string.h]]> to erase sensitive data, where memory store must always be performed regardless of optimizations.^[6]
• Add [[memccpy]] function in <string.h> to efficiently concatenate strings – similar to POSIX and SVID C extensions.^[7]
• Add [[strdup]] and strndup functions in <string.h> to allocate a copy of a string – similar to POSIX and SVID C extensions.^[8]
• Add memalignment function in <[[stdlib.h]]> to determine the byte alignment of a pointer.^[9]
• 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.^[10]
  • In the following, replace * with uc, us, ui, ul, ull for five function names, or blank for a type-generic macro.^[10]
  • Add stdc_count_ones* and stdc_count_zeros* to count number of 1 or 0 bits in value.^[10]
  • Add stdc_leading_ones* and stdc_leading_zeros* to count leading 1 or 0 bits in value.^[10]
  • Add stdc_trailing_ones* and stdc_trailing_zeros* to count trailing 1 or 0 bits in value.^[10]
  • Add stdc_first_leading_one* and stdc_first_leading_zero* to find first leading bit with 1 or 0 in value.^[10]
  • Add stdc_first_trailing_one* and stdc_first_trailing_zero* to find first trailing bit with 1 or 0 in value.^[10]
  • 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).^[10]
  • Add stdc_bit_floor* to determine the largest integral power of 2 that is not greater than value.^[10]
  • Add stdc_bit_ceil* to determine the smallest integral power of 2 that is not less than value.^[10]
  • Add stdc_bit_width* to determine number of bits to represent a value.^[10]
• Add timegm function in <[[time.h]]> to convert time structure into calendar time value - similar to function in glibc and musl libraries.^[11]
• New <[[math.h]]> functions based on IEEE 754-2019 recommendations, such as trigonometry functions operating on units of

\pi x and exp10.^[12]

Existing functions

• Add %b binary conversion specifier to printf function family.^[13]
• Add %b binary conversion specifier to scanf function family.^[13]
• Add 0b and 0B binary conversion support to strtol and wcstol function families.^[13]
• Make the functions [[bsearch]], [[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.^[14]

Preprocessor

• Add and directives,^[15] which are essentially equivalent to and . Both directives were added to C++23 standard and GCC 12.^[16]
• Add directive for binary resource inclusion and allowing the availability of a resource to be checked by preprocessor directives.^[17]
• Add directive for diagnostics.^[18]
• Add allowing the availability of a header to be checked by preprocessor directives.^[19]
• Add allowing the availability of an attribute to be checked by preprocessor directives.^[20] (see "C++ compatibility" group for new attribute feature)
• Add functional macro for variadic macros which expands to its argument only if a variadic argument has been passed to the containing macro.^[21]

Types

• Add, a null pointer type.
• Add and types for bit-precise integers. Add macro for maximum bit width.^{[22] [23]}
• Add ckd_add, ckd_sub, ckd_mul macros for checked integer operations.^[24]
• Variably-modified types (but not VLAs which are automatic variables allocated on the stack) become a mandatory feature.^[25]
• Better support for using [[Const_(computer_programming)|const]] with arrays.^[26]
• Standardization of the [[typeof]](...) operator.^[27]
• The meaning of the 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).^[28]
• Compatibility rules for structure, union, and enumerated types were changed to allow a redeclaration of a compatible type with the same tag.^[29]
• Exact-width integer may now exceed (N2888).^[30]

Constants

• Add constant for nullptr_t type.^[31]
• Add wb and uwb integer literal suffixes for and types,^[32] such as yields an unsigned _BitInt(3), and yields a signed _BitInt(4) which has three value bits and one sign bit.
• Add 0b and 0B binary literal constant prefixes,^[33] such as (equating to 0xAA).
• Add ' digit separator to literal constants,^[34] such as (equating to 0xFEDCBA98), (equating to 299792458), (equating to 1.414213562).
• Add the ability to specify the underlying type of an [[enumerated type|enum]].^[35]
• Allow s with no fixed underlying type to store values that are not representable by .^[36]

Keywords

• Add and keywords.^[37]
• Add,,,, keywords. Previously defined keywords become alternative spellings:,,,, .^[38]
• Add keyword (see "types" group)
• Add and keywords (see "types" group)
• Add keyword (see "constants" group)
• Add keyword (see "other" group)
• Add,, keywords for (optional) decimal floating-point arithmetic (see "other" group)

Syntax

• Labels can appear before declarations and at the end of compound statements.^[39]
• Unnamed parameters in function definitions.^[40]
• Zero initialization with {} (including initialization of VLAs).^[41]
• Variadic functions no longer need a named argument before the ellipsis and the macro no longer needs a second argument nor does it evaluate any argument after the first one if present.^[42]
• Add C++11 style attribute syntax^[43] using double square brackets . In addition to C++11 attributes listed below, add new attributes:
  • <nowiki>[[unsequenced]]</nowiki>^[44] allows compiler optimizations for functions producing repeatable outputs only based on their parameters
  • <nowiki>[[reproducible]]</nowiki>, similar to <nowiki>[[unsequenced]]</nowiki>, but for functions whose call order also matters
• Add single-argument [[Assert.h#static assert|_Static_assert]] for compatibility with C++17.^[45]
• Functions with no arguments listed in the prototype void foo are understood as taking no arguments (see removal of K&R function declarations)

C++ compatibility

• 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, [[Assert.h#static assert|_Static_assert]] (see Syntax). For labels at the end of compound statements a corresponding change was made to C++23.^[46]
• Add C++-style attributes (see Syntax). Add attributes ^[47],^[48],^[49],^[50],^[51] and attribute for compatibility with C++11, then deprecate,, header <stdnoreturn.h> features introduced in C11.^[52] Duplicate attributes are allowed for compatibility with C++23.^[53] All standard attributes can also be surrounded by double underscores (e.g. is equivalent to).
• Add u8 prefix for character literals to represent UTF-8 encoding for compatibility with C++17.^{[54] [55]}
• Add and preprocessing directives for compatibility with C++23.^[15] (see "preprocessor" group)

Other features

• 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.^{[56] [57]}
• The [[constexpr]] specifier for objects but not functions, unlike C++'s equivalent.^[58]
• Add type for storing UTF-8 encoded data and change the type of u8 character constants and string literals to . 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.^[59]
• Clarify that all strings and literals shall be UTF-16 encoded, and all strings and literals shall be UTF-32 encoded, unless otherwise explicitly specified.^[60]
• Allow storage class specifiers to appear in compound literal definition.^[61]

Obsolete features

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

• Remove trigraphs.^[62]

• Remove K&R function definitions/declarations (with no information about the function arguments).^{[63] [64]}

• Remove representations for signed integers other than two's complement. Two's complement signed integer representation will be required.^[65]

• The macros in <float.h> are obsolescent features.^[66]

Compiler support

The GCC 9,^[67] Clang 9.0,^[68] and Pelles C 11.00^[69] compilers implement an experimental compiler flag to support this standard.

See also

• 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++

Further reading

• N3096 (working draft of C23 standard); WG14; April 2023. (free download)
• N3149 (working draft of C23 standard); WG14; July 2023. (not available to public)
• N3219 (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)

External links

• C Language WG14 (Working Group 14)

• WG14 Document Repository

• WG14 Meetings - agenda and minutes

• WG14 Charters: C2x Charter, C23 Charter, Interpreting the C23 Charter, C Standard Charter

Notes and References

1. Web site: History of C . cppreference.com . https://web.archive.org/web/20221019191546/https://en.cppreference.com/w/c/language/history . October 19, 2022 . 2022-06-27 . live.
2. Web site: WG14-N2086: C2x Charter . open-std.org . https://web.archive.org/web/20221222213708/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2086.htm . December 22, 2022 . 2016-09-20 . live.
3. Web site: WG14-N3156: Updated C23 Schedule . open-std.org . https://web.archive.org/web/20240129010357/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3156.pdf . January 29, 2024 . 2023-07-19 . live.
4. Web site: WG14-N2437: Agenda for October 2019 . open-std.org . https://web.archive.org/web/20210305073426/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2437.htm . March 5, 2021 . 2019-10-21 . live.
5. Web site: WG14-N3096: Draft for ISO/IEC 9899:2024 . open-std.org . https://web.archive.org/web/20230402172459/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3096.pdf . April 2, 2023 . April 1, 2023 . live.
6. Web site: WG14-N2897: memset_explicit . open-std.org . https://web.archive.org/web/20221025074215/https://open-std.org/jtc1/sc22/wg14/www/docs/n2897.htm . October 25, 2022 . 2021-12-27 . live.
7. Web site: WG14-N2349: Toward more efficient string copying and concatenation . open-std.org . https://web.archive.org/web/20220930092258/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2349.htm . September 30, 2022 . 2019-03-18 . live.
8. Web site: WG14-N2353: strdup and strndup . open-std.org . https://web.archive.org/web/20221224063709/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2353.htm . December 24, 2022 . 2019-03-18 . live.
9. Web site: WG14-N2974: Queryable pointer alignment . open-std.org . https://web.archive.org/web/20221013182240/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n2974.pdf . October 13, 2022 . 2022-04-15 . live.
10. Web site: WG14-N3022: Modern Bit Utilities . open-std.org . https://web.archive.org/web/20221224194734/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3022.htm . December 24, 2022 . 2022-07-06 . live.
11. Web site: WG14-N2833: Add timegm as non-optional part of time.h . open-std.org . https://web.archive.org/web/20211201062452/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2833.htm . December 1, 2021 . 2021-10-07 . live.
12. See N3096 § B.11 for a useful overview. The functions were added in separate documents: N2488, its updated versions, and its refs.
13. Web site: WG14-N2630: formatted input/output of binary integer numbers . open-std.org . https://web.archive.org/web/20221214154315/https://open-std.org/JTC1/SC22/WG14/www/docs/n2630.pdf . December 14, 2022 . 2021-01-01 . live.
14. Web site: WG14-N3020: Qualifier-preserving standard library functions . open-std.org . https://web.archive.org/web/20221013190826/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n3020.pdf . October 13, 2022 . 2022-06-13 . live.
15. Web site: WG14-N2645: Add support for preprocessing directives #elifdef and #elifndef . open-std.org . https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2645.pdf . November 28, 2022 . 2020-01-25 . live.
16. Web site: GCC 12 Adds Support For New #elifdef #elifndef Directives . phoronix . https://web.archive.org/web/20221227050002/https://www.phoronix.com/news/GCC-12-elifdef-elifndef . December 27, 2022 . May 12, 2021 . live.
17. Web site: WG14-N3017: #embed - a scannable, tooling-friendly binary resource inclusion mechanism . open-std.org . https://web.archive.org/web/20221224045304/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm . December 24, 2022 . 2022-06-27 . live.
18. Web site: WG14-N2686: #warning . open-std.org . https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2686.pdf . November 28, 2022 . 2022-07-22 . live.
19. Web site: WG14-N2799: __has_include for C . open-std.org . https://web.archive.org/web/20221224103617/https://open-std.org/JTC1/SC22/WG14/www/docs/n2799.pdf . December 24, 2022 . 2021-08-30 . live.
20. Web site: WG14-N2553: Querying attribute support . open-std.org . https://web.archive.org/web/20221014221314/https://open-std.org/JTC1/SC22/WG14/www/docs/n2553.pdf . October 14, 2022 . 2020-08-04 . live.
21. Web site: WG14-N3033: Comma omission and comma deletion . open-std.org . https://web.archive.org/web/20221227031727/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3033.htm . December 27, 2022 . 2022-07-20 . live.
22. Web site: WG14-N2763: Adding a Fundamental Type for N-bit integers . open-std.org . https://web.archive.org/web/20221227055250/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2763.pdf . December 27, 2022 . 2021-06-21 . live.
23. Web site: WG14-N3035: _BitInt Fixes . open-std.org . https://web.archive.org/web/20221013182206/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n3035.pdf . October 13, 2022 . 2022-07-21 . live.
24. Web site: WG14-N2867: Checked N-Bit Integers . open-std.org . https://web.archive.org/web/20221214154907/https://open-std.org/JTC1/SC22/WG14/www/docs/n2867.pdf . December 14, 2022 . 2021-11-28 . live.
25. Web site: WG14-N2778: Variably-Modified Types . open-std.org . https://web.archive.org/web/20221222053411/https://open-std.org/jtc1/sc22/wg14/www/docs/n2778.pdf . December 22, 2022 . 2021-07-11 . live.
26. Web site: WG14-N2607: Compatibility of Pointers to Arrays with Qualifiers . open-std.org . https://web.archive.org/web/20221013182946/https://www.open-std.org/jtc1/sc22/WG14/www/docs/n2607.pdf . October 13, 2022 . 2020-10-31 . live.
27. Web site: WG14-N2899: Not-so-magic - typeof for C . open-std.org . https://web.archive.org/web/20221224044528/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2899.htm . December 24, 2022 . 2022-01-21 . live.
28. Web site: WG14-N3007: Type inference for object definitions . open-std.org . https://web.archive.org/web/20221224105654/https://open-std.org/JTC1/SC22/WG14/www/docs/n3007.htm . December 24, 2022 . 2022-06-10 . live.
29. Web site: WG14-N3037: Improved Rules for Tag Compatibility (updates N3032) .
30. Web site: C23 is Finished: Here is What is on the Menu . The Pasture . en . 31 July 2022.
31. Web site: WR14-N3042: Introduce the nullptr constant . open-std.org . https://web.archive.org/web/20221224043228/https://open-std.org/JTC1/SC22/WG14/www/docs/n3042.htm . December 24, 2022 . 2022-07-22 . live.
32. Web site: WG14-N2775: Literal suffixes for bit-precise integers . open-std.org . https://web.archive.org/web/20221227014728/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2775.pdf . December 27, 2022 . 2021-07-13 . live.
33. Web site: WG14-N2549: Allow for binary integer constants . open-std.org . https://web.archive.org/web/20221222192818/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2549.pdf . December 22, 2022 . 2020-07-30 . live.
34. Web site: WG14-N2626: Digit separators . open-std.org . https://web.archive.org/web/20221219215425/https://open-std.org/JTC1/SC22/WG14/www/docs/n2626.pdf . December 19, 2022 . 2020-12-15 . live.
35. Web site: WG14-N3030: Enhancements to Enumerations . open-std.org . https://web.archive.org/web/20221126132709/https://open-std.org/JTC1/SC22/WG14/www/docs/n3030.htm . November 26, 2022 . 2022-07-19 . live.
36. Web site: WG14-N3029: Improved Normal Enumerations . open-std.org . https://web.archive.org/web/20230129180341/https://open-std.org/JTC1/SC22/WG14/www/docs/n3029.htm . January 29, 2023 . 2022-07-19 . live.
37. Web site: WG14-N2935: Make false and true first-class language features . open-std.org . https://web.archive.org/web/20221121123457/https://open-std.org/JTC1/SC22/WG14/www/docs/n2935.pdf . November 21, 2022 . 2022-02-15 . live.
38. Web site: WG14-N2934: Revise spelling of keywords . open-std.org . https://web.archive.org/web/20221224132455/https://open-std.org/JTC1/SC22/WG14/www/docs/n2934.pdf . December 24, 2022 . 2022-02-15 . live.
39. Web site: WG14-N2508: Free Positioning of Labels Inside Compound Statements . open-std.org . https://web.archive.org/web/20221227183107/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2508.pdf . December 27, 2022 . 2020-03-28 . live.
40. Web site: WG14-N2510: Allowing unnamed parameters in a function definition . open-std.org . https://web.archive.org/web/20221224075948/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2510.pdf . December 24, 2022 . 2020-04-09 . live.
41. Web site: WG14-N2900: Consistent, Warningless, and Intuitive Initialization with . open-std.org . https://web.archive.org/web/20221227181452/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2900.htm . December 27, 2022 . 2022-01-01 . live.
42. Web site: WG14-N2975: Relax requirements for variadic parameter lists . open-std.org . https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2975.pdf . November 28, 2022 . 2022-04-15 . live.
43. Web site: WG14-N2335: Attributes in C . open-std.org . https://web.archive.org/web/20221026060722/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2335.pdf . October 26, 2022 . 2019-03-09 . live.
44. Web site: Unsequenced functions . 2024-07-18 . open-std.org.
45. Web site: WG14-N2265: Harmonizing static_assert with C++ . open-std.org . https://web.archive.org/web/20230328064918/https://open-std.org/JTC1/SC22/WG14/www/docs/n2265.pdf . March 28, 2023 . 2018-07-06 . live.
46. Web site: Labels at the end of compound statements (C compatibility). 2022-01-13.
47. Web site: WG14-N2554: Minor attribute wording cleanups . open-std.org . https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2554.pdf . November 28, 2022 . 2020-08-04 . live.
48. Web site: WG14-N2334: The deprecated attribute . open-std.org . https://web.archive.org/web/20221019131835/https://open-std.org/JTC1/SC22/WG14/www/docs/n2334.pdf . October 19, 2022 . 2019-01-22 . live.
49. Web site: WG14-N2408: The fallthrough attribute . open-std.org . https://web.archive.org/web/20221225070709/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2408.pdf . December 25, 2022 . 2019-08-11 . live.
50. Web site: WG14-N2270: The maybe_unused attribute . open-std.org . https://web.archive.org/web/20221225070836/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2270.pdf . December 25, 2022 . 2018-07-06 . live.
51. Web site: WG14-N2267: The nodiscard attribute . open-std.org . https://web.archive.org/web/20221019131846/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2267.pdf . October 19, 2022 . 2018-07-06 . live.
52. Web site: WG14-N2764: The noreturn attribute . open-std.org . https://web.archive.org/web/20221225063437/https://open-std.org/JTC1/SC22/WG14/www/docs/n2764.pdf . December 25, 2022 . 2021-06-21 . live.
53. Web site: WG14-N2557: Allow Duplicate Attributes . open-std.org . https://web.archive.org/web/20221128133337/https://open-std.org/JTC1/SC22/WG14/www/docs/n2557.pdf . November 28, 2022 . 2020-09-01 . live.
54. Web site: WG14-N2418: Adding the u8 character prefix . open-std.org . https://web.archive.org/web/20230113210023/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2418.pdf . January 13, 2023 . 2019-09-02 . live.
55. 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.
56. Web site: WG14-N2341: ISO/IEC TS 18661-2 - Floating-point extensions for C - Part 2: Decimal floating-point arithmetic . open-std.org . https://web.archive.org/web/20221121122559/https://open-std.org/JTC1/SC22/WG14/www/docs/n2341.pdf . November 21, 2022 . February 26, 2019 . live.
57. Web site: WG14-N2601: Annex X - IEC 60559 interchange and extended types . open-std.org . https://web.archive.org/web/20221014221322/https://open-std.org/JTC1/SC22/WG14/www/docs/n2601.pdf . October 14, 2022 . October 15, 2020 . live.
58. Web site: WG14-N3018: The constexpr specifier for object definitions . open-std.org . https://web.archive.org/web/20221224074302/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3018.htm . December 24, 2022 . 2022-07-06 . live.
59. Web site: WG14-N2653: char8_t: A type for UTF-8 characters and strings (Revision 1) . open-std.org . https://web.archive.org/web/20230527110842/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2653.htm . May 27, 2023 . 2021-06-04 . live.
60. Web site: WG14-N2728: char16_t & char32_t string literals shall be UTF-16 & UTF-32 . open-std.org . https://web.archive.org/web/20230527110756/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2728.htm . May 27, 2023 . 2021-05-15 . live.
61. Web site: WG14-N3038: Introduce storage-class specifiers for compound literals . open-std.org . https://web.archive.org/web/20221126130057/https://open-std.org/JTC1/SC22/WG14/www/docs/n3038.htm . November 26, 2022 . 2022-07-21 . live.
62. Web site: WG14-N2940: Removing trigraphs??! . open-std.org . https://web.archive.org/web/20221026005747/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2940.pdf . October 26, 2022 . 2022-03-02 . live.
63. Web site: WG14-N2432: Remove support for function definitions with identifier lists proposal . open-std.org . https://web.archive.org/web/20221227012244/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2432.pdf . December 27, 2022 . September 25, 2019 . live.
64. Web site: WG14-N2841: No function declarators without prototypes . open-std.org . https://web.archive.org/web/20221112154740/https://www9.open-std.org/jtc1/sc22/wg14/www/docs/n2841.htm . November 12, 2022 . 2021-10-10 . live.
65. Web site: WG14-N2412: Two's complement sign representation . open-std.org . https://web.archive.org/web/20221227174224/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2412.pdf . December 27, 2022 . August 11, 2019 . live.
66. Web site: WG14-N2993: Make *_HAS_SUBNORM be obsolescent . open-std.org . https://web.archive.org/web/20221205194635/https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2993.htm . December 5, 2022 . 2022-06-06 . live.
67. Web site: GCC 9 Release Notes . GNU Project . https://web.archive.org/web/20221227032646/https://gcc.gnu.org/gcc-9/changes.html . December 27, 2022 . live.
68. Web site: Clang 9.0 - add new language mode for C2x . LLVM Project Repository . https://web.archive.org/web/20221227032640/https://github.com/llvm/llvm-project/commit/d06f3917913d2558b771ccc48d838f8cd8993c01 . December 27, 2022 . May 14, 2019 . live.
69. Web site: Pelles C - major changes between 10.00 and 11.00 . smorgasbordet.com . https://web.archive.org/web/20221227032644/http://www.smorgasbordet.com/pellesc/changes_1000_1100.htm . December 27, 2022 . live.