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

[Andrew Pinski]

> bug 21334 seems to deal with multiple threads accessing the same shared object
> at the same time.  However, the sample code provided here involves separate
> private objects so there should not be any such issues.  If it is not possible
> to assume that separate threads can access unrelated STL objects at the same
> time, then this would imply that all STL operations (regardless of the object)
> must be serialized!

The empty string is the same object really.

-- Pinski