[Bug libstdc++/21334] Lack of Posix compliant thread safety in std::basic_string

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21334

--- Comment #51 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is no longer an issue when using the new non-reference-counted std::string
implementation in GCC 5.