https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- More precisely, <string> includes <bits/localefwd.h> which declares (but does not define) the overload of std::isblank.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- More precisely, <string> includes <bits/localefwd.h> which declares (but does not define) the overload of std::isblank.