microsoft
P3370R1 Add C23 `<stdbit.h>` And `<stdckdint.h>`
WG21-P3370R1 Add C23 <stdbit.h> And <stdckdint.h>
No feature-test macro is mentioned.
While this is primarily something for the UCRT to implement (as <cmeow> wrapper headers aren't being added), this is also updating the std.compat module, so STL changes will be required.
Note: We're focused on implementing the remaining library-only features in C++23. Until that's done, we will NOT be accepting PRs for C++26 features.
nullptr is also part of C23 (https://open-std.org/JTC1/SC22/WG14/www/docs/n3042.htm) missing from ucrt. hope it's on their radar along with /std:c23 support https://learn.microsoft.com/cpp/build/reference/std-specify-language-standard-version?view=msvc-170
