https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64467
--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> --- In the POSIX (i.e. "C") locale it should only be space and tab, but implementing that when the target only has 8-bits for the ctype mask and doesn't have a blank class is very difficult. For other locales it's OK for newline to be in the blank class.
