[Bug libstdc++/91910] Debug mode: there is a racing condition between destructors of iterator and the associated container.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91910

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk only for now but I might backport it.