[Bug libstdc++/81092] Missing symbols for new std::wstring constructors

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81092

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |7.2

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This was introduced by r239773.

I think we should fix it for 7.2 and bump the symbol versions for trunk.