namespace std {
template<> struct char_traits<char>;
template<> struct char_traits<char8_t>;
template<> struct char_traits<char16_t>;
template<> struct char_traits<char32_t>;
template<> struct char_traits<wchar_t>;
}
The header
defines five specializations of the class template
char_traits:
char_traits<char>,
char_traits<char8_t>,
char_traits<char16_t>,
char_traits<char32_t>,
and
char_traits<wchar_t>.