They are library functions for which a good library does not exist. I recently needed to convert probably-UTF-8 data to definitely valid UTF-8 with errors repl

They are library functions for which a good library does not exist. I recently needed to convert probably-UTF-8 data to definitely valid UTF-8 with errors replaced. This was not an enjoyable experience in C++. (The ztd proposal is IMO a big step in the right direction.)