[Bug-hurd] Re: defining _POSIX_SYNCHRONOUS_IO although msync not available?

[Roland McGrath]

> is it posixly correct to define _POSIX_SYNCHRONIZED_IO although we don't
> support msync?

No, I don't think it is (from looking at 1003.1-1996).  That is, if
_POSIX_MAPPED_FILES and _POSIX_SYNCHRONIZED_IO are both defined, msync is
supposed to work.  However, _POSIX_MAPPED_FILES means you have mmap et al;
so it's useful to define that since we do.  _POSIX_SYNCHRONIZED_IO means
fsync and fdatasync work, so it's useful to define that since they do.
If we want to pedanticly comply, probably _POSIX_SYNCHRONIZED_IO is the one
that should go.