27 Strings library [strings]

27.2 Character traits [char.traits]

27.2.4 char_traits specializations [char.traits.specializations]

27.2.4.1 General [char.traits.specializations.general]

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 <string> 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>.