_Back             118 maint/gnulib/lib/fpurge.c   fp->_Rback = fp->_Back + sizeof (fp->_Back);
_Back              85 maint/gnulib/lib/freadahead.c             ? (fp->_Back + sizeof (fp->_Back)) - fp->_Rback
_Back              94 maint/gnulib/lib/fseeko.c       && fp->_Rback == fp->_Back + sizeof (fp->_Back)