[Bug libstdc++/56166] std::string::clear() can throw despite being marked noexcept

[fasdfasdas at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56166

--- Comment #8 from Tolga <fasdfasdas at gmail dot com> ---
Correction, removing the copy, therefore reference counting effect, feels like
has decreased the error but I found out std::string::clear() still throws
std::length_error, although I use no reference.