Re: Unable to read history on latest Cygwin

[Peter Stephenson <pws@csr.com>]

On Thu, 17 Dec 2009 12:00:25 -0800
Wayne Davison <wayned@users.sourceforge.net> wrote:
> On Wed, Dec 16, 2009 at 7:54 AM, Wayne Davison <4wayned@gmail.com> wrote:
> 
> > According to various web docs, symlinks are atomic on NFS, so that might be
> > a good thing to use in general (replacing the use of link()).
> >
> 
> Attached is my patch for adding preferential use of a symlink as the locking
> mechanism.  This should interoperate just fine with a hard-link creating
> locker, but sadly, will have issues if another locker is using open with
> O_EXCL.  I've made the symlink name "/pid-$PID/host-$HOST" in an attempt to
> make a create (open) over an existing symlink fail with an error (unless the
> /pid-$PID dir happens to exist and is writable).  We could try to add
> O_NOFOLLOW (when available) to the O_EXCL-open as well.  However, hopefully
> no system will exist where one zsh locker is trying to use open-locking and
> another is trying to use a link-locking idiom.
> 
> What do you think?  Dangerous?  Useful?

(I moved this to zsh-workers.)

What about the historical behaviour of zsh?  Are there old versions of the
shell that might do something inconsistent with this?  This is not a
typical problem for most users, anyway, but it would be good not to stir
things up unnecessarily.

Other than that I can't think of any aspect that looks particularly
dangerous.  We could limit this to both HAVE_LINK and HAVE_SYMLINK to
ensure it didn't change the behaviour on systems without link()---slightly
illogical but unlikely to be a real limitation on the most common systems.

-- 
Peter Stephenson <pws@csr.com>            Software Engineer
Tel: +44 (0)1223 692070                   Cambridge Silicon Radio Limited
Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, UK


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