bug#5649: 23.1.92; Indentation problems in C mode

[Michael Welsh Duggan]

Alan Mackenzie <acm@muc.de> writes:

> Hi, Michael and Yidong
>
> On Fri, Feb 26, 2010 at 07:12:06PM -0500, Chong Yidong wrote:
>> Michael Welsh Duggan <mwd@cert.org> writes:
>
>> > I'm getting some screwy indentation behavior from C mode.  From a
>> > current bzr checkout/install of emacs, try the following recipe:
>
>> > emacs -Q foo.c                 | starts emacs on foo.c (included below)
>> > C-u 7 C-n                      | move down 7 lines
>> > TAB                            | indent, nothing changes (good)
>> > C-p C-p                        | move up 2 lines
>> > TAB C-n TAB C-n                | indent 2 lines, nothing changes (good)
>> > TAB                            | line unindents by 2 (bad)
>> > TAB                            | line re-indents (good, but strange)
>> > TAB                            | no change this time
>
>> Thanks.  This is a regression vs Emacs 23.1, so we should definitely fix
>> it before releasing Emacs 23.2.
>
>> I can reproduce the bug with the Emacs 23.0.90, so it's be around since
>> at lease 12-09 last year.  However, I haven't yet had the time to do a
>> proper bisect.
>
> I've just committed the folowing patch, which should fix the bug:

I'm afraid this causes a much more serious bug.  Recipe:

emacs -Q
Open a new C-mode file.  Then type the following:
#if FOO
#endif

int bar;

For me the following happens:  The #endif is not fontified.  The "int
bar" is not fontified.  The semicolon causes an error.  I have verified
that reverting the patch below goes back to the old behavior, so this
patch is what is causing the bug.


> === modified file 'lisp/progmodes/cc-engine.el'
> --- lisp/progmodes/cc-engine.el       2010-02-25 21:21:25 +0000
> +++ lisp/progmodes/cc-engine.el       2010-03-01 11:23:59 +0000
> @@ -2641,7 +2641,8 @@
>       ;; (car c-state-cache).  There can be no open parens/braces/brackets
>       ;; between `good-pos'/`good-pos-actual-macro-start' and (point-max),
>       ;; due to the interface spec to this function.
> -     (setq pos (if good-pos-actual-macro-end
> +     (setq pos (if (and good-pos-actual-macro-end
> +                        (> in-macro-start good-pos-actual-macro-start))
>                     (1+ good-pos-actual-macro-end) ; get outside the macro as
>                                       ; marked by a `category' text property.
>                   good-pos))
>
>
> Thanks for the clean and concise bug report!

-- 
Michael Welsh Duggan
(mwd@cert.org)