[Bug libstdc++/79820] std::ifstream sets errno to zero

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79820

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-03-02
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think we should capture the previous value of errno and restore it. I thought
I checked for all places this was needed but maybe I only looked in the include
and src sub-directories, not the config one.