std::char_traits<char>::eof, std::char_traits<wchar_t>::eof, std::char_traits<char8_t>::eof, std::char_traits<char16_t>::eof, std::char_traits<char32_t>::eof
From cppreference.com
                    
                                        
                    < cpp | string | char traits
                    
                                                            
                    |   static int_type eof();  | 
 (constexpr since C++11) (noexcept since C++11)  | 
|
Returns a value not equivalent to any valid value of type char_type.
See CharTraits for the general requirements on character traits for X::eof.
Parameters
(none)
Return value
 char_type 
 | 
eof() | 
|---|---|
| char | EOF | 
| wchar_t | WEOF | 
| char8_t | an implementation-defined constant that cannot appear as a valid UTF-8 code unit  | 
| char16_t | an implementation-defined constant that cannot appear as a valid UTF-16 code unit  | 
| char32_t | an implementation-defined constant that cannot appear as a Unicode code point  | 
Complexity
Constant.
See also
|    [static]  | 
  checks whether a character is eof value  (public static member function)  |