FWIW, wchar_t is guaranteed to be Unicode if __STDC_ISO_10646__ is defined, which is the case on Linux/glibc. It's too bad that other platforms are lagging behind on this - there's really no good reason to not guarantee this in 2024. Windows at least has the excuse of having wchar_t be 16-bit which they can't change for legacy compat reasons, but that doesn't explain why e.g. FreeBSD isn't there yet.