Re: Kludge in eval.c

[Eli Zaretskii <eliz@gnu.org>]

> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Date: Sun, 11 Dec 2016 13:36:25 -0500
> 
> > When I worked on merging the concurrency branch, I bumped into a
> > problem with the recently introduced watcher feature.  The problem is
> > that variables can have thread-local bindings, so when there's a
> > thread switch, Emacs needs to rebind those variables to the values
> > they have in the new thread.  If such a variable is marked as
> > trap-write, rebinding would normally call the watchers, which I think
> > is not what we want.  Do you agree?
> 
> Yes, I agree. The fact that thread-local values are implemented by
> rebinding is a C level implementation detail that shouldn't leak into
> Lisp code.
> 
> >
> > If you agree, then we need a way of bypassing the watchers call when
> > the rebinding is due to a thread switch.  In the merged concurrency
> > code I used a semi-kludgey solution for that, see the two FIXMEs I
> > left behind, in rebind_for_thread_switch and unbind_for_thread_switch.
> > Could you please look at that and suggest a cleaner solution?
> >
> 
> The easiest is adding a global flag, but after doing that, I realized
> adding a parameter to set_internal and friends isn't too much trouble.
> So my suggestion is the attached v2 patch, I've included the v1 for
> comparison, since I had written it already anyway.

Thanks, please push your v2.