Re: Fixing parallel byte-compilation

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 13 Sep 2010 09:33:21 -0700 (PDT)
> From: "Davis Herring" <herring@lanl.gov>
> Cc: emacs-devel@gnu.org
> 
> > ! 		  ;; The old code used to: delete target-file before
> > ! 		  ;; writing it, so that any hard-links continue to
> > ! 		  ;; point to the old file (this makes it possible
> > ! 		  ;; for installed files to share disk space with
> > ! 		  ;; the build tree, without causing problems when
> > ! 		  ;; emacs-lisp files in the build tree are
> > ! 		  ;; recompiled).  Renaming works the same way.
> > ! 		  (write-region (point-min) (point-max) tempfile)
> > ! 		  (rename-file tempfile target-file t))
> 
> Does `rename-file' work outside of POSIX (that is, on Windows) if the
> target file exists?

Not for free, but it does.  Windows has sys_rename, which see in
w32.c, while the DOS build uses a standard C library whose `rename'
does that under the hood.

Of course, this could still fail if the target is open by some other
program, but the old code uses delete-file which would fail in that
case as well.  So we didn't make the situation worse than it was
already.