I reviewed the core changes of the patch. I don't think we need
mb_string_info() at all. Instead, we can just call pg_mbxxx() functions.
I rewrote the patch to use pg_mbstrlen_with_len() and pg_mbcharcliplen().
What do you think the changes? It requires re-counting lengths of multi-byte
strings in some cases, but the code will be much simpler and can avoid
allocating length buffers.
I'd like to apply contrib/stringinfo apart from the core changes,
because there seems to be still some idea to improve sprintf().
--
Itagaki Takahiro
