C++20 with u8, char8_t and std::string

In addition to @lubgr’s answer, the paper char8_t backward compatibility remediation (P1423) discusses several ways how to make std::string with char8_t character arrays.

Basically the idea is that you can cast the u8 char array into a “normal” char array to get the same behaviour as C++17 and before, you just have to be a bit more explicit. The paper discusses various ways to do this.

The most simple (but not fully zero overhead, unless you add more overloads) method that fits your usecase is probably the last one, i.e. introduce explicit conversion functions:

std::string from_u8string(const std::string &s) {
  return s;
}
std::string from_u8string(std::string &&s) {
  return std::move(s);
}
#if defined(__cpp_lib_char8_t)
std::string from_u8string(const std::u8string &s) {
  return std::string(s.begin(), s.end());
}
#endif