| Macro | description | 
|---|---|
| __STD_UTF_16__ | If defined, values of type char16_t have UTF-16 encoding. Otherwise, the encoding of char16_t is unspecified. (In C11, the macro expands to 1 when defined) | 
| __STD_UTF_32__ | If defined, values of type char32_t have UTF-32 encoding. Otherwise, the encoding of char32_t is unspecified. (In C11, the macro expands to 1 when defined) |