debugging post command hook max-lisp-eval-depth

[John Shahid <jvshahid@gmail.com>]

Hi all,

every now and then my Emacs will get in a bad state because of some
infinite recursion in the post-command-hook. I am reaching out for ideas
on how to debug Emacs when it gets into this weird state. Keep in mind
that it is hard to do anything with Emacs at that point since any
command (switching buffer, starting debugger) will fail with the same
error `Lisp nesting exceeds...'.

I don't know when this started happening and can't easily debug/bisect
my configuration since this situation happens rarely and intermittently
(2 or 3 times last week).

What I currently have is the following post-command-hook in init.el (not
sure how useful it will be) to stop the infinite recursion:

    (defvar debug-post-command-hook-count nil)

    (defun debug-post-command-hook ()
      (let ((debug-post-command-hook-count (1+ (or debug-post-command-hook-count 0))))
        (if (> debug-post-command-hook-count 10)
            (debug)
          (print (format "post-command-hook %d %S"
                         debug-post-command-hook-count
                         (current-buffer))
                 #'external-debugging-output))))

    (add-hook 'post-command-hook #'debug-post-command-hook)

I also compiled emacs with no optimization and debug symbols (using info
in etc/DEBUG) and planning to use `xbacktrace' when I run into that
situation.

Do you have any other ideas to prepare me for when this happens again ?

p.s. my emacs version is "4a7e74fea687011ee81dcbb02294bccd99b3a05f". I
tried to use the latest commit but ran into weird issues during
redisplay (where Emacs would end up in die()) and autocompletion (where
the candidates left edge isn't lined up properly), but I decided to
ignore those issues for now and stick with the previous revision.

-js