question about "Making change-major-mode-hook buffer-local while locally let-bound!"

["Drew Adams" <drew.adams@oracle.com>]

I use a modified definition of `pp-display-expression' that binds these two
hooks to nil around the call (emacs-lisp-mode), to prevent the hooks from
running:

(let ((emacs-lisp-mode-hook    nil)
      (change-major-mode-hook  nil))
  (emacs-lisp-mode))

That is the only change - otherwise, emacs -Q.

(No, I do not remember just why I added the c-m-m-h binding (years ago), but I
probably did so because of some problem or annoyance the hook sometimes caused.)

The c-m-m-h binding now results in this message being displayed:

"Making change-major-mode-hook buffer-local while locally let-bound!"

Question:
What is the right way to prevent these hooks from running here?

Do I need to use remove-hook followed by add-hook: saving, emptying and
repopulating the hook? What's the right approach?

---

Also, out of curiosity, where is `change-major-mode-hook' being made
buffer-local?  Grepping the lisp sources shows only these hits that seem to
involve making it local:

gnus/gnus-msg.el:449: (gnus-make-local-hook 'change-major-mode-hook)
arc-mode.el:771: (set (make-local-variable 'change-major-mode-hook)
'archive-desummarize)

But arc* and gnus* are not present in `features'.  A wild guess suggests maybe
something in font-lock is the culprit (emacs -Q shows `(font-lock-change-mode
t)' as the local value), but I haven't found anything.  I didn't find anything
by skimming the C code either.

GNU Emacs 24.0.50.1 (i386-mingw-nt5.1.2600)
 of 2010-06-14 on 3249CTO