[Bug libstdc++/81522] c++17/old-abi/cygwin empty stringstream invalid memory access

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81522

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Possibly related to PR 82172 (which was due to a binutils bug) but that
apparently only occurs when using LTO.