https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118105
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #0) > "AÀÁÂÃÄÅaàáâãäå" should all produce the same primary sort key. Whether this is true or not depends on the locale, but also the string literal encoding. When using UTF-8 most of those characters are not a single byte, and so std::regex is completely incapable of dealing with them. The regex "[[=À=]]" will throw an exception if the literal encoding is UTF-8.
