On Wed, Oct 12, 2022 at 9:02 PM Thiago Macieira via Std-Proposals <std-proposals@lists.isocpp.org> wrote:

[ ...]
 
C has the same constraint since C11, but Unicode strings and characters are
optional there, so the constraint is optional.
 
C has required CHAR_BIT >= 8 since C89 (e.g., C89 requires UCHAR_MAX >= 255).