20 Strings library [strings]

20.5 Null-terminated sequence utilities [c.strings]

20.5.5 Header <cuchar> synopsis [cuchar.syn]

namespace std {
  using mbstate_t = see below;
  using size_t = see [support.types.layout];

  size_t mbrtoc8(char8_t* pc8, const char* s, size_t n, mbstate_t* ps);
  size_t c8rtomb(char* s, char8_t c8, mbstate_t* ps);
  size_t mbrtoc16(char16_t* pc16, const char* s, size_t n, mbstate_t* ps);
  size_t c16rtomb(char* s, char16_t c16, mbstate_t* ps);
  size_t mbrtoc32(char32_t* pc32, const char* s, size_t n, mbstate_t* ps);
  size_t c32rtomb(char* s, char32_t c32, mbstate_t* ps);
}
The contents and meaning of the header <cuchar> are the same as the C standard library header <uchar.h>, except that it declares the additional mbrtoc8 and c8rtomb functions and does not declare types char16_­t nor char32_­t.
See also: ISO C 7.28