What is the STDC_VERSION value for C11? asks about C11, and How can I use “nullptr” for null pointers prior to C23? says that the current versions of GCC and Clang define it to a placeholder value 202000L.

GCC 14 Release Series Changes, New Features, and Fixes has now added the std=c23 flag, but doesn’t mention what __STDC_VERSION__ expands to.