[Bug libstdc++/32261] Thread race segfault in std::string::append with -O and -s

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32261

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
For the record, I believe this was fixed by https://gcc.gnu.org/r67912