Re: Lisp watchpoints

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 22 Nov 2015 15:13:47 -0500
> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Cc: Eli Zaretskii <eliz@gnu.org>, John Wiegley <jwiegley@gmail.com>, emacs-devel@gnu.org
> 
> Okay, I think I have something mostly working now. The first patch
> adds watchpoints, then the following 2 implement lisp debug on
> variable set, and ensure redisplay, respectively. The debugger part
> isn't quite right, I'm seeing it trigger a 2nd time after continuing.

Thanks.

Is it possible to have watchers that don't require a Funcall, or avoid
exposing the watcher function to Lisp to begin with?  Funcall can GC,
so the usability of such watchers for internal purposes might be
limited in some situations.

How about allowing special, say, integer values for a watcher, which
will then cause a call to a C function from a table indexed by the
watcher value?  Or something else to that effect.

Another comment is: do we care about scalability of property lists for
storing watchers?

The debug command might be more mnemonic (at least for me ;-) if it
were called 'debug-watch', or maybe 'debug-set-watchpoint'.  A similar
command for Edebug would also be nice.

Thanks again for working on this.

P.S. We should decide whether we ad this to the emacs-25 branch or to
master.