bug#13046: 23.4; Minimal Example to freeze emacs C++ mode (nasty interaction between templates & windows endline characters )

[John Smith <drefleladi@gmail.com>]

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Hello all,

I'm afraid my limited emacs knowledge will not allow me to test the patch.
(Building fresh from source + patching the lisp => too much :) )
I trust however that it does!

Thanks for being so responsive.

Yours Sincerely,
John

On Sun, Dec 2, 2012 at 7:16 PM, Alan Mackenzie <acm@muc.de> wrote:

> Hello Yidong, Vadim, John.
>
> On Sun, Dec 02, 2012 at 10:13:47AM +0800, Chong Yidong wrote:
> > John Smith <drefleladi@gmail.com> writes:
>
> > > Using emacs -Q,just open the attached minimal example and try typing
> > > "std::string" in the body of the function.
> > > That should hang emacs forever (or at least it does on my up-to-date
> > > ubuntu).
>
> > I think this is a duplicate of Bug#11841.
>
> > The patch posted in Bug#11841 does not completely fix this test case.
> > Giving ^M whitespace syntax in CC mode, as Stefan suggested, seems like
> > the easiest solution.  Alan, could you take another look?  It would be
> > good to have this fixed in Emacs 24.3.
>
> On Wed, Jul 25, 2012 at 11:58:22PM +0300, Vadim K wrote:
> > Hello Alan,
>
>
> > I've tried your patch and it worked fine for the original posted
> > bad.cpp file. However I have found a variation of that file that still
> > causes emacs to hang (see attached bad2.cpp).
> [ Bug #11841 ]
>
>
> I think the enclosed patch fixes these bugs.  Please try out the patch
> and let us know if there are still any problems here.
>
> The basic problem is that (forward-comment -1) doesn't recognise a CR
> character as whitespace.  My first attempt to patch this, in July, was
> only partly successful.
>
> The specific problem was that (forward-comment -1) _sometimes_ goes back
> over the LF in CRLF, sometimes not.  I've not discovered by what
> criterion.
>
>
>
> diff -r 1adcc48506f9 cc-engine.el
> --- a/cc-engine.el      Sun Apr 22 09:42:29 2012 +0000
> +++ b/cc-engine.el      Sun Dec 02 17:46:53 2012 +0000
> @@ -1454,8 +1454,21 @@
>             ;; return t when moving backwards at bob.
>             (not (bobp))
>
> -           (if (let (open-paren-in-column-0-is-defun-start)
> -                 (forward-comment -1))
> +           (if (let (open-paren-in-column-0-is-defun-start moved-comment)
> +                 (while
> +                     (and (not (setq moved-comment (forward-comment -1)))
> +                     ;; Cope specifically with ^M^J here -
> +                     ;; forward-comment sometimes gets stuck after ^Ms,
> +                     ;; sometimes after ^M^J.
> +                          (or
> +                           (when (eq (char-before) ?\r)
> +                             (backward-char)
> +                             t)
> +                           (when (and (eq (char-before) ?\n)
> +                                      (eq (char-before (1- (point))) ?\r))
> +                             (backward-char 2)
> +                             t))))
> +                 moved-comment)
>                 (if (looking-at "\\*/")
>                     ;; Emacs <= 20 and XEmacs move back over the
>                     ;; closer of a block comment that lacks an opener.
>
>
>
> --
> Alan Mackenzie (Nuremberg, Germany).
>

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