GCC Preparing To Set C23 "GNU23" As Default C Language Version

The GNU Compiler Collection (GCC) support for the C23 programming language standard is now considered "essentially feature-complete" with GCC 15. As such they are preparing to enable the C23 language version (using the GNU23 dialect) by default for the C language version of GCC when not otherwise specified.

Preparations are now underway to set the default C language version of GCC to GNU23 as the GNU dialect of C23. Or in other words, implying -std=gnu23 when no other C standard is specified.

Joseph Myers of Red Hat sent out a patch to begin preparing for the -std=gnu23 default.

"Now that C23 support is essentially feature-complete, I'd like to switch the default language version for C compilation to -std=gnu23.

This requires updating a large number of testcases that fail with the new language version if left unchanged. In this patch, update most of the tests for which there is a safe change that works both before and after the update to default language version - typically adding the option -std=gnu17 or -Wno-old-style-definition to the tests..."

Jakub Jelinek of Red Hat's compiler team as well separately started this mailing list thread today for updating the compiler support page on cppreference.com for reflecting the latest C23/GNU23 additions to GCC. There are a few C23 features currently marked as unimplemented in GCC 15 but their status is being pursued.

So it's looking like soon GCC could be setting C23/GNU23 as its default C language version. It's in mid-November when GCC 15 "stage one" feature development is wrapping up to focus on bug-fixing ahead of GCC 15.1 stable debuting early next year.