[Bug libstdc++/123100] std::ostringstream:str() (r-value version) returns garbage

[terra at gnome dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123100

--- Comment #7 from M Welinder <terra at gnome dot org> ---
> What do you expect this to do?
> "Effects: implementation-defined, except that setbuf(0, 0) has no effect."

I expect the writes from then on to go into buf.  And that is indeed what
happens with gcc and that has been the case for decades.  I understand that
leaving to a different library could leave with with a bleeding foot.

This is perhaps not the nicest part of the library's design