bug#53136: 28.0.90; segfault in lock_file

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  53136@debbugs.gnu.org
> Date: Tue, 11 Jan 2022 08:51:25 +0800
> 
> > 3. More importantly, I'm sure there are other places where Emacs
> > assumes that errno values are positive. I doubt whether it's
> > reasonable to expect Emacs developers to remember and work around this
> > Haiku incompatibility, every time they call a function that sets errno
> > or returns an errno value. Instead, we should arrange for Haiku builds
> > to use positive errno values, they way errno behaves on GNU and other
> > POSIX-compatible hosts. This should be a much more maintainable
> > solution.
> 
> I would prefer for us to find and fix those instances manually, because
> B_USE_POSITIVE_POSIX_ERRORS is some kind of stopgap measure for porting
> POSIX utilities like sshfs, and prevents some other functionality from
> working correctly (i.e. apparently it's an error to -ltracker with it
> defined, so file dialogs won't work.)

Ugh!

Fixing each place individually is a time bomb: no one will remember
that after enough time has passed, and we will add bugs.

The only alternative is to filter errno via some macro, which will do
nothing on all platforms but Haiku, where it will map them to Posix
values.  Butt-ugly, but it's not our fault.