https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65928
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> --- It seems normal to me. There are now several functions called isblank in namespace std, and the compiler doesn't know which one to pick when you don't give it a hint (like you do for myblank). A more explicit diagnostic would be nice though.
