Annex C (informative) Compatibility [diff]

C.8 C standard library [diff.library]

C.8.3 Modifications to definitions [diff.mods.to.definitions]

C.8.3.1 Types char16_t and char32_t [diff.char16]

The types char16_t and char32_t are distinct types rather than typedefs to existing integral types.
The tokens char16_t and char32_t are keywords in C++ ([lex.key]).
They do not appear as macro or type names defined in <cuchar>.