[Bug libstdc++/51813] [4.7 Regression] -fvisibility=hidden causes std::codecvt members to be undefined

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51813

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-01-13 
16:43:12 UTC ---
(In reply to comment #3)
> What do we want to do about C library visibility?

We can't redeclare all the types with default visibility, because we don't know
if e.g. mbstate_t is just a typedef.

This appears to fix it, but would it need to be done for any explicit
instantation relying on non-builtin types defined outside libstdc++?

  extern template
    __attribute__((visibility("default")))
    const codecvt<wchar_t, char, mbstate_t>&
    use_facet<codecvt<wchar_t, char, mbstate_t> >(const locale&);