Re: Fontifying-errors make Emacs (mostly) unusable

[Thorsten Jolitz <tjolitz@googlemail.com>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> Thats probably because the error appears in a (fontifying) hook
>> function thats called before any real action.
>> How can I get out of this 'trap' without restarting Emacs?
>
> Depends on the specific problem you're encountering, but it may very
> well be that kill&restart is the only way to fix it.
>
> Due to Emacs's extensive reliance of "modifiable Elisp code", it's
> generally impossible to prevent such situations.
>
> There is code in various parts of Emacs to try and handle some
> particular cases (e.g. an error in a pre-command-hook will cause Emacs
> to remove that function from the hook), so if you can give details about
> your particular case and it seems to be a common enough problem, maybe
> we can find a way to make Emacs behave more gracefully.

Ok, here is a recipe to reproduce the error: 

0. with fully functional emacs, get markdown.el (via package manager)
   and make a copy of it (marktest.el)
1. (re)start "emacs -Q"
2. open file marktest.el
3. comment out this defun (at line 1954):

;; (defun markdown-fontify-buffer-wiki-links ()
;;   "Refontify all wiki links in the buffer."
;;   (interactive)
;;   (markdown-check-change-for-wiki-link (point-min) (point-max) 0))


4. save and eval-buffer (or load marktest.el)
5. find (new empty) file test.md
6. put it in markdown-mode (M-x markdown-mode)

#Bang#

'Symbol is void...' error message
try M-x, M-:, C-x d, nothing works, you are trapped. 

-- 
cheers,
Thorsten