History file locking (was Re: 4.3.4-dev-4 and 4.2.6-dev-2 available)

[Peter Stephenson <pws@xxxxxxx>]

(Move this to zsh-workers since this is now development only.)

Vincent Lefevre wrote:
> I've undone Wayne's patch zsh-users/8494 that didn't seem to work
> anyway and retried my patch, and while I got history corruption
> with the unpatched version a few minutes before (as usual), I can't
> reproduce the corruption with my patched version.

We can probably add your stuff as an option; I'm a bit worried about
forcing fcntl() locking on everybody willy nilly.  This probably needs
to wait till after 4.3.5 otherwise that will never get out at this rate.

> However, I get the following error when I quit the shell:
> 
> zsh: failed to write history file /home/vlefevre/.zhistory: bad file descript
> or
> 
> but nothing is missing in the history!

It's possible there's an overagressive test for a write failure; I added
some more after reports of problems.  You might be able to track down
where this is coming from fairly easily.

pws