http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49745
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-07-14 11:01:26 UTC --- the problem is actually in gthr-posix.h no libstdc++ header includes <unistd.h> except <ext/stdio_syn_filebuf.h> which is a non-standard extension and so that's not a problem
