bug#30350: 27.0.50; Newest master can't run processes on macOS

[Alan Third]

On Sun, Feb 04, 2018 at 09:28:12PM +0000, Philipp Stephani wrote:
> Alan Third <alan@idiocy.org> schrieb am So., 4. Feb. 2018 um 22:12 Uhr:
> 
> > On Sun, Feb 04, 2018 at 09:06:15PM +0000, Alan Third wrote:
> > > Oddly if you do
> > >
> > >     (file-accessible-directory-p "/usr/bin/true")
> > >
> > > it works correctly, but then once you run
> > >
> > >     (call-process "/usr/bin/true")
> > >
> > > file-accessible-directory-p incorrectly returns true on subsequent
> > > calls. Paul’s commit didn’t make any real changes to
> > > file-accessible-directory-p so I suspect this problem is older.
> >
> > In fact, I can replicate it on Emacs 25, so it’s an old bug.
> >
> >
> This is then a different bug; could you report it as a new one?

It’s actually all the same bug. Paul’s change made file-directory-p
use file-accessible-directory-p, and it’s playing up.

It looks like the root cause is faccessat returning 0 for
‘/usr/bin/true/.’ when it should probably be returning -1.
-- 
Alan Third