Re: cwarn/font-lock problem under HP-UX 10.20

[Klaus Zeitler]

>>>>> "Eli" == Eli Zaretskii <eliz@is.elta.co.il> writes:
    Eli>
    Eli> On Mon, 3 Dec 2001, Klaus Zeitler wrote:
    Eli>
    >> 1. start emacs with -q
    >> 2. M-x: global-font-lock-mode
    >> 3. in scratch buffer execute (add-hook 'c-mode-hook 'turn-on-cwarn-mode)
    >> 4. load e.g. the following buggy C file:
    >>
    >> 1  main ()
    >> 2  {
    >> 3    int x=5;
    >> 4    if (x=1);
    >> 5    {
    >> 6    }
    >> 7  }
    >>
    >> 5. in line 4 the "=" and the ";" should be highlighted with
    >> font-lock-warning face, but they aren't
    >>
    >> 6. turn off cwarn-mode and turn it on again with twice
    >> M-x cwarn-mode
    >> now line 4 is correctly highlighted
    >>
    >>
    >> When I execute the first 4 steps on my GNU/Linux PC line 4 is
    >> correctly highlighted, but not under HP-UX. I'm puzzled, this
    >> is the first time that syntax highlighting acts differently on
    >> two OS.
    Eli>
    Eli> It's not system-dependent, I can reproduce it on MS-Windows at least.
    Eli> I'm gueqsing that you have something on GNU/Linux that happens even in
    Eli> "emacs -q" (have you tried "emacs -q --no-site-file"?).
    Eli>
    Eli> There's probably some subtle problem with regexps used by cwarn.
    Eli> Could you please look?
no, --no-site-file doesn't change anything. I think it has something to do
with (font-lock-add-keywords nil ...).
The local variable font-lock-keywords doesn't contain the cwarn keywords when
the hook is used (under HP-UX 10.20 that is, and I'm pretty sure it'll work on
my GNU/Linux PC, I'll check tonight). I tried to debug this, but once I set
debug-on-entry to cwarn-font-lock-add-keywords everything works.

I've fixed it now by changing the last line in cwarn-font-lock-add-keywords

(defun cwarn-font-lock-add-keywords (&optional mode)
  "Install keywords into major MODE, or into current buffer if nil."
  (dolist (pair cwarn-font-lock-feature-keywords-alist)
    (let ((feature (car pair))
          (keywords (cdr pair)))
      (if (not (listp keywords))
          (setq keywords (symbol-value keywords)))
      (if (cwarn-is-enabled (or mode major-mode) feature)
          (font-lock-add-keywords mode keywords)))))

to

(defun cwarn-font-lock-add-keywords (&optional mode)
  "Install keywords into major MODE, or into current buffer if nil."
  (dolist (pair cwarn-font-lock-feature-keywords-alist)
    (let ((feature (car pair))
          (keywords (cdr pair)))
      (if (not (listp keywords))
          (setq keywords (symbol-value keywords)))
      (if (cwarn-is-enabled (or mode major-mode) feature)
          (font-lock-add-keywords (or mode major-mode) keywords)))))

now it works. But I remember vaguely that Stefan Monnier mentioned something
about not using (font-lock-add-keywords 'some-mode ...) and he recommended
(font-lock-add-keywords nil ...) in the mode-hook instead.

Klaus

-- 
 ------------------------------------------
|  Klaus Zeitler      Lucent Technologies  |
|  Email:             kzeitler@lucent.com  |
 ------------------------------------------
---
The shortest distance between two points
is under construction.   -- Noelie Alito