Bug? in CC-Mode

Bug? in CC-Mode

[Matthieu Lemerre]

Hi,

I used to have a (c-set-style "gnu") in my .emacs, which was useless
but everything worked fine.

When I tried emacs22 I had the following problem: c-set-style calls
c-set-style-1, which calls c-setup-paragraph-variables, which sets
globally paragraph-start, which is annoying for many reasons. Normally
paragraph-start is local to the buffer, but the call to c-set-style
change its value before it becomes buffer-local.

Should this be considered as a bug?

Thanks,
Matthieu

Re: Bug? in CC-Mode

[Alan Mackenzie]

Matthieu Lemerre <racin@free.fr> wrote on Tue, 07 Jun 2005 15:00:38 +0200:
> Hi,

> I used to have a (c-set-style "gnu") in my .emacs, which was useless
> but everything worked fine.

> When I tried emacs22 I had the following problem: c-set-style calls
> c-set-style-1, which calls c-setup-paragraph-variables, which sets
> globally paragraph-start, which is annoying for many reasons. Normally
> paragraph-start is local to the buffer, but the call to c-set-style
> change its value before it becomes buffer-local.

> Should this be considered as a bug?

Yes, definitely!

Normally, when you initialise a CC Mode buffer, the initialisation
process gets to call `c-basic-common-init', which contains the form
(make-local-variable 'paragraph-start).

So, at a guess, you're calling `c-set-style' in an unusual way, a way
that by-passes the normal initialisation sequence.  Would you please show
us exactly how and where you're calling `c-set-style', so that we can fix
the bug (or fix the documentation ;-).  

Thanks in advance!

> Matthieu

-- 
Alan Mackenzie (Munich, Germany)
Email: aacm@muuc.dee; to decode, wherever there is a repeated letter
(like "aa"), remove half of them (leaving, say, "a").

Re: Bug? in CC-Mode

[Matthieu Lemerre]

Alan Mackenzie <acm@muc.de> writes:

> Matthieu Lemerre <racin@free.fr> wrote on Tue, 07 Jun 2005 15:00:38
> +0200:
>> Hi,
>
>> I used to have a (c-set-style "gnu") in my .emacs, which was useless
>> but everything worked fine.
>
>> When I tried emacs22 I had the following problem: c-set-style calls
>> c-set-style-1, which calls c-setup-paragraph-variables, which sets
>> globally paragraph-start, which is annoying for many
> reasons. Normally
>> paragraph-start is local to the buffer, but the call to c-set-style
>> change its value before it becomes buffer-local.
>
>> Should this be considered as a bug?
>
> Yes, definitely!

OK. I wasn't sure because it wasn't the normal way to call
c-set-style.

>
> Normally, when you initialise a CC Mode buffer, the initialisation
>process gets to call `c-basic-common-init', which contains the form
>(make-local-variable 'paragraph-start).
>
> So, at a guess, you're calling `c-set-style' in an unusual way, a way
> that by-passes the normal initialisation sequence.  Would you please
> show
> us exactly how and where you're calling `c-set-style', so that we can
> fix
> the bug (or fix the documentation ;-).  


I can reproduce the bug by just evaluating (c-set-style "gnu") in a
fresh emacs session (launched with emacs -q) with eval-expression.  It
also works when CC-mode is already loaded, if I do this in a different
fundamental mode (like the *scratch* buffer.)

I had nothing surrounding the (c-set-style "gnu") of my .emacs.  I may
have read c-set-style documentation too quickly.


The faulting lines start line 501 of cc-styles.el: 

(setq paragraph-start (concat comment-line-prefix
				  c-paragraph-start
				  "\\|"
				  page-delimiter)
	  paragraph-separate (concat comment-line-prefix
				     c-paragraph-separate
				     "\\|"
				     page-delimiter)
	  paragraph-ignore-fill-prefix t
	  adaptive-fill-mode t
	  adaptive-fill-regexp
	  (concat comment-line-prefix
		  (if (default-value 'adaptive-fill-regexp)
		      (concat "\\("
			      (default-value 'adaptive-fill-regexp)
			      "\\)")
		    "")))


I tried also a (c-set-style "gnu" t) (setting the dont-override
optional parameter to t) but it does the same thing.


I use Debian GNU/Linux, and the bug can be reproduced by both using an
emacs-snapshot debian package or a recent CVS checkout.


I am interrested in knowing what would be the correct solution : would
it be to check if paragraph-start is buffer-local before setting it?
Or a more complicated scheme?





Thanks,

Matthieu

Re: Bug? in CC-Mode

[Kevin Rodgers]

Matthieu Lemerre wrote:
 > I am interrested in knowing what would be the correct solution : would
 > it be to check if paragraph-start is buffer-local before setting it?
 > Or a more complicated scheme?

Don't call it outside of a CC Mode buffer, i.e. only call it within a
mode hook:

(add-hook 'c-mode-hook (lambda () (c-set-style "gnu")))

BTW, the manual says: The default style in all newly created buffers is
`gnu', but you can change this by setting variable `c-default-style'.
So you shouldn't need to do anything to get the GNU style.

-- 
Kevin Rodgers