C17 (C standard revision)

Last updated August 04, 2025

C17, formally ISO/IEC 9899:2018,^[1] is an open standard for the C programming language, prepared in 2017 and published 5-Jul-2018.^[1] It replaced C11 (standard ISO/IEC 9899:2011),^[2] and is superseded by C23 (ISO/IEC 9899:2024) since October 2024.^[3] Since it was under development in 2017, and officially published in 2018, C17 is sometimes referred to as C18.^[4]

Changes from C11

C17 fixes numerous minor defects in C11 without introducing new language features.^[2]

The __STDC_VERSION__ macro is increased to the value 201710L.

For a detailed list of changes from the previous standard, see Clarification Request Summary for C11. Examples of changes include fixes for #elif, realloc, and typos, among others.^[5]

Compiler support

List of compilers supporting C17:

GCC 8.1.0^[6]
LLVM Clang 7.0.0^[7]
IAR EWARM v8.40.1^[8]
Microsoft Visual C++ VS 2019 (16.8)^[9]
Pelles C 9.00^[10]

References

1 2 "ISO/IEC 9899:2018 - Information technology -- Programming languages -- C". International Organization for Standardization. Archived from the original on 1 April 2025. Retrieved 16 April 2025.
1 2 "The Standard - C". www.iso-9899.info.
↑ "WG 14 Document log". www.open-std.org.
↑ "Using the GNU Compiler Collection (GCC): C Dialect Options". gcc.gnu.org.
↑ ISO/IEC JTC1/SC22/WG14 (October 2017). "Clarification Request Summary for C11 Version 1.13". www.open-std.org. Retrieved 28 September 2020.{{cite web}}: CS1 maint: numeric names: authors list (link)
↑ "Using the GNU Compiler Collection (GCC): C Dialect Options". gcc.gnu.org.
↑ "Clang 7 documentation — Clang Compiler User's Manual".
↑ "IAR Information Center for Arm - Release notes". netstorage.iar.com.
↑ "C11 and C17 Standard Support Arriving in MSVC". devblogs.microsoft.com. 14 September 2020.
↑ "Changelog - Added support for new C17 standard". www.smorgasbordet.com/pellesc/.

External links

C Language WG14 (Working Group 14)

Preceded by C11	C language standards	Succeeded by C23

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[ISO2018-1] 1 2 "ISO/IEC 9899:2018 - Information technology -- Programming languages -- C". International Organization for Standardization. Archived from the original on 1 April 2025. Retrieved 16 April 2025.

[iso-9899info-2] 1 2 "The Standard - C". www.iso-9899.info.

[3] "WG 14 Document log". www.open-std.org.

[4] "Using the GNU Compiler Collection (GCC): C Dialect Options". gcc.gnu.org.

[5] ISO/IEC JTC1/SC22/WG14 (October 2017). "Clarification Request Summary for C11 Version 1.13". www.open-std.org. Retrieved 28 September 2020.{{cite web}}: CS1 maint: numeric names: authors list (link)

[6] "Using the GNU Compiler Collection (GCC): C Dialect Options". gcc.gnu.org.

[7] "Clang 7 documentation — Clang Compiler User's Manual".

[8] "IAR Information Center for Arm - Release notes". netstorage.iar.com.

[9] "C11 and C17 Standard Support Arriving in MSVC". devblogs.microsoft.com. 14 September 2020.

[10] "Changelog - Added support for new C17 standard". www.smorgasbordet.com/pellesc/.

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Category

C17 (C standard revision)

Contents

Changes from C11

Compiler support

See also

References

Further reading

External links