Convert between std::u8string and std::string

Question

C++20 added char8_t and std::u8string for UTF-8. However, there is no UTF-8 version of std::cout and OS APIs mostly expect char

Answer 1

At present, std::c8rtomb and std::mbrtoc8 are the the only interfaces provided by the standard that enable conversion between the execution encoding and UTF-8. The interfaces are awkward. They were designed to match pre-existing interfaces like std::c16rtomb and std::mbrtoc16. The wording added to the C++ standard for these new interfaces intentionally matches the wording in the C standard for the pre-existing related functions (hopefully these new functions will eventually be added to C; I still need to pursue that). The intent in matching the C standard wording, as confusing as it is, is to ensure that anyone familiar with the C wording recognizes that the char8_t interfaces work the same way.

cppreference.com has some examples for the UTF-16 versions of these functions that should be useful for understanding the char8_t variants.

• https://en.cppreference.com/w/cpp/string/multibyte/mbrtoc16
• https://en.cppreference.com/w/cpp/string/multibyte/c16rtomb