bug#3808: 23.1.50; CC-mode: Impossible to set c-cleanup-list

[Alan Mackenzie <acm@muc.de>]

Hi, Jan!

On Sun, Jul 12, 2009 at 12:33:01PM +0200, Jan Djärv wrote:


> Alan Mackenzie skrev:
> >Hi, Jan!

> >On Fri, Jul 10, 2009 at 01:14:45PM +0200, Jan D. wrote:
> >>I customize c-cleanup-list.  This is then the full contents of my
> >>.emacs:
> >>(custom-set-variables
> >>  ;; custom-set-variables was added by Custom.
> >>  ;; If you edit it by hand, you could mess it up, so be careful.
> >>  ;; Your init file should contain only one such instance.
> >>  ;; If there is more than one, they won't work right.
> >> '(c-cleanup-list (quote (scope-operator space-before-funcall))))
> >>(custom-set-faces
> >>  ;; custom-set-faces was added by Custom.
> >>  ;; If you edit it by hand, you could mess it up, so be careful.
> >>  ;; Your init file should contain only one such instance.
> >>  ;; If there is more than one, they won't work right.
> >> )

> >>I start emacs with --no-site-file, open a .c-file.

> >Just done this, in a new userid, having copied your .emacs.  To be sure,
> >I tried on a freshly updated CVS Emacs.

> >>Check the value of c-cleanup-list:

> >>c-cleanup-list is a variable defined in `cc-vars.el'.
> >>Its value is (scope-operator)

> >I can't reproduce the problem; I get:

> >    Its value is
> >    (scope-operator space-before-funcall)

> >, just as desired.

> >>Local in buffer xftfont.c; global value is 
> >>(scope-operator space-before-funcall)

> >Well, that looks OK.  :-)

> >Might it be that there's a local variables section at the end of
> >xftfont.c which is overriding c-cleanup-list?

> No, but since this is in the emacs source tree, there is a .dir-locals.el
> at the root of the source tree, and that comes in effect.  So it is not 
> that it doesn't work, it is just this situation (setting c-file-style as a 
> file local variable has the same effect).

<MASSIVE GROAN>  Ohhh nooooooo.  I wasn't aware of this .dir-locals.el
facility.  I suppose I should have been - it's been discussed on
emacs-devel before now.  Complexity upon complexity!  Who needs this?
Who wants it?

> So what happens is:
> c-mode sets style to GNU.
> My customization is applied.
> .dir-locals.el sets style to GNU, thus erasing my customization.

The bug would appear to be the time at which these directory level
customisations are done.

I think it makes some sort of sense for _file_ local variables to be
highest priority - It's a fairly rare thing, only done for a particular
need, and if somebody specifies a particular setting of, say,
`c-cleanup-list' in the file locals, there'll be a damn good reason for
it.

But directory level?  Surely they are of LOWEST priority - to have them
overriding things set in hooks etc., is insanity.

> >>And indeed, space-before-funcall is not in effect.  It seems impossible to
> >>set this variable.  I also tried setting c-old-style-variable-behavior to 
> >>t,
> >>but it made no difference.

> >>The manual needs to explain how to set variables in a manner that works,
> >>an example with lisp to add to .emacs would be nice also.

> >"The manual" being the CC Mode manual, of course.  In the appendix
> >"Sample .emacs File", there's an example of c-cleanup-list being set in a
> >style.  The instructions on how to set "style variables" in general (of
> >which c-cleanup-list is one) are on the page "Configuration Basics" and
> >its sup-page "Style Variables".

> >So I think the information is there, but perhaps it's not easy enough to
> >find.  Could you, perhaps, reconstruct how you went about looking for the
> >info?  Maybe the manual needs an extra hint or two somewhere.  Thanks!


> The situation above, i.e. how to preserve my customization when 
> .dir-locals.el or file variables are in effect is not described.

Yes.  In the case of file local variables, the FM states (page "Config
Basics") that they supersede settings made in other ways.  This is surely
their point - they're intended for rare (high priority) use.  For
example, you might want to use a different style (C style, as described
on page "Styles" in the fine manual) for a particular source file that
was imported from somewhere else, so as not to cause masses of
reformatting diffs.

> I tried the mode hook, it didn't work either.  Is there a c-set-style hook?

Now, you're being sarcastic here, aren't you?  PLEASE tell me you're
being sarcastic.  :-)  (Note, I don't blame you.  I would be too, in your
position.)

I'll bring this matter up on emacs-devel.  Bare with me!

> 	Jan D.

-- 
Alan Mackenzie (Nuremberg, Germany).