GNU bug report logs - #13467
24.3.50; Problem with `advice' show-paren-function

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: nyc4bos <at> aol.com
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50; Problem with `advice' show-paren-function
Date: Wed, 16 Jan 2013 17:22:56 -0500

Hi,

While trying to send an email message ^C^C `(message-send-and-exit)',
I got the following error message in the echo area:

Error in timer: (wrong-type-argument characterp nil)

I was not able to send the message and could only abort (^G).

I then got a backtrace which I have included (below).

I suspect this is because of the changes to `advice'.

Here is 'advice' function that I am using:

(defadvice show-paren-function (after show-matching-paren-offscreen
                                      activate)
  "If the matching paren is offscreen, show the matching line in the
echo area. Has no effect if the character before point is not of
the syntax class ')'."
  (interactive)
  (let ((matching-text nil))
    ;; Only call `blink-matching-open' if the character before point
    ;; is a close parentheses type character. Otherwise, there's not
    ;; really any point, and `blink-matching-open' would just echo
    ;; "Mismatched parentheses", which gets really annoying.
    (if (char-equal (char-syntax (char-before (point))) ?\))
        (setq matching-text (blink-matching-open)))
    (if (not (null matching-text))
        (message matching-text))))

Thanks.

Debugger entered--Lisp error: (wrong-type-argument characterp nil)
  char-syntax(nil)
  (char-equal (char-syntax (char-before (point))) 41)
  (if (char-equal (char-syntax (char-before (point))) 41) (setq matching-text (blink-matching-open)))
  (let ((matching-text nil)) (if (char-equal (char-syntax (char-before (point))) 41) (setq matching-text (blink-matching-open))) (if (not (null matching-text)) (message matching-text)))
  (let (ad-return-value) (setq ad-return-value (with-no-warnings (funcall ad--addoit-function))) (let ((matching-text nil)) (if (char-equal (char-syntax (char-before (point))) 41) (setq matching-text (blink-matching-open))) (if (not (null matching-text)) (message matching-text))) ad-return-value)
  ad-Advice-show-paren-function(#[nil
  "\203\336`\306\307`S!!\310=\203





In GNU Emacs 24.3.50.1 (i386-mingw-nt6.1.7601)
 of 2013-01-15 on ODIEONE
Bzr revision: 111532 dmantipov <at> yandex.ru-20130115101431-o6w1qeqwqcmyxmi9
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -IC:/Devel/emacs/build/include --ldflags -LC:/Devel/emacs/build/lib'

Important settings:
  value of $LANG: en_US
  locale-coding-system: cp1252
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu> 
<send-emacs-bug-report>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

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None found.

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multi-tty emacs)

Message #8 received at 13467 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: nyc4bos <at> aol.com
Cc: 13467 <at> debbugs.gnu.org
Subject: Re: bug#13467: 24.3.50; Problem with `advice' show-paren-function
Date: Wed, 16 Jan 2013 17:39:33 -0500

nyc4bos <at> aol.com wrote:

>     (if (char-equal (char-syntax (char-before (point))) ?\))

What do you expect this do if called eg at point-min?
Maybe fail with wrong-type-argument characterp nil?

Message #11 received at 13467 <at> debbugs.gnu.org (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: "'Glenn Morris'" <rgm <at> gnu.org>, <nyc4bos <at> aol.com>
Cc: 13467 <at> debbugs.gnu.org
Subject: RE: bug#13467: 24.3.50; Problem with `advice' show-paren-function
Date: Wed, 16 Jan 2013 14:46:39 -0800

> >     (if (char-equal (char-syntax (char-before (point))) ?\))
> 
> What do you expect this do if called eg at point-min?
> Maybe fail with wrong-type-argument characterp nil?

E.g.,

(let ((matching-text nil)
      (cb            (char-before (point))))
  (when (and cb  (char-equal (char-syntax cb) ?\) ))
    (setq matching-text  (blink-matching-open)))
  (when matching-text (message matching-text)))

Message #16 received at 13467 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: "Drew Adams" <drew.adams <at> oracle.com>
Cc: 'Glenn Morris' <rgm <at> gnu.org>, nyc4bos <at> aol.com, 13467 <at> debbugs.gnu.org
Subject: Re: bug#13467: 24.3.50; Problem with `advice' show-paren-function
Date: Wed, 16 Jan 2013 18:37:58 -0500

> (let ((matching-text nil)
>       (cb            (char-before (point))))
>   (when (and cb  (char-equal (char-syntax cb) ?\) ))
>     (setq matching-text  (blink-matching-open)))
>   (when matching-text (message matching-text)))

Aka

   (let* ((cb (char-before (point)))
          (matching-text
           (when (and cb  (char-equal (char-syntax cb) ?\) ))
             (blink-matching-open))))
     (when matching-text (message matching-text)))


-- Stefan "always try to give the right value right away"

Message #19 received at 13467 <at> debbugs.gnu.org (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: "'Stefan Monnier'" <monnier <at> iro.umontreal.ca>
Cc: 'Glenn Morris' <rgm <at> gnu.org>, nyc4bos <at> aol.com, 13467 <at> debbugs.gnu.org
Subject: RE: bug#13467: 24.3.50; Problem with `advice' show-paren-function
Date: Wed, 16 Jan 2013 16:04:45 -0800

> > (let ((matching-text nil)
> >       (cb            (char-before (point))))
> >   (when (and cb  (char-equal (char-syntax cb) ?\) ))
> >     (setq matching-text  (blink-matching-open)))
> >   (when matching-text (message matching-text)))
> 
> Aka
> 
>    (let* ((cb (char-before (point)))
>           (matching-text
>            (when (and cb  (char-equal (char-syntax cb) ?\) ))
>              (blink-matching-open))))
>      (when matching-text (message matching-text)))
>
> -- Stefan "always try to give the right value right away"

Yes.  Aka:

(let* ((cb (char-before (point)))
       (matching-text (and cb
                           (char-equal (char-syntax cb) ?\) )
                           (blink-matching-open))))
  (when matching-text (message matching-text)))

-- Drew "use `and' for value; use `when' for effect",
   who tried to keep things close to the OP code, to start

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