[Bug libstdc++/85729] including c++ headers within extern "C" linkage specification

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85729

--- Comment #4 from nsz at gcc dot gnu.org ---
(In reply to Jonathan Wakely from comment #3)
> Does that fix it?

yes, thanks.