LLVM Clang Now Supports -std=c23

LLVM/Clang developers have been working on C23 language support for some time already but to this point it's only been exposed when using the -std=c2x target or -std=gnu2x for the GNU dialect. However, with C2x having been finalized this summer as C23, the LLVM Clang 18 compiler will now honor the -std=c23 option.

Merged to LLVM Git yesterday for what will be Clang 18 is honoring the -std=c23 and -std=gnu23 options. The existing -std=c2x and -std=gnux2x options will continue to work with the Clang compiler. Now that this next C revision was finalized at the June 2023 WG14 meeting and that the informal name of the standard will be C23 regardless of the year ISO publishes it, LLVM developers are fine with calling it "C23" now.

The Clang status page shows many of the C23 features already being in place for this open-source C compiler while some feature work does remain.

The already-branched LLVM Clang 17 is due for release in September while LLVM Clang 18 should debut as stable around next March, shortly before the release of the GCC 14.1 compiler. Hopefully for Clang 18 we'll see the C23 support ironed out.