Implicit instantiation of undefined template 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >' Implicit instantiation of undefined template 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >' ios ios

Implicit instantiation of undefined template 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >'


You need to include this header:

#include <string>