GNU bug report logs - #54218
[PATCH] Magic number regexp shouldn't match beyond end-of-line.

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

From: "Andrew L. Moore" <slewsys <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Cc: "Andrew L. Moore" <slewsys <at> gmail.com>
Subject: [PATCH] Magic number regexp shouldn't match beyond end-of-line.
Date: Tue, 1 Mar 2022 23:52:50 -0500

Repeat magic number search to work around match-data loss
when `save-window-excursion' is called.
---
 lisp/progmodes/executable.el | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lisp/progmodes/executable.el b/lisp/progmodes/executable.el
index d7c093444e..9116bdea9d 100644
--- a/lisp/progmodes/executable.el
+++ b/lisp/progmodes/executable.el
@@ -232,7 +232,8 @@ executable-set-magic
       (save-excursion
        (goto-char (point-min))
        (add-hook 'after-save-hook 'executable-chmod nil t)
-       (if (looking-at "#![ \t]*\\(.*\\)$")
+        ;; Regexp shouldn't match beyond end-of-line.
+       (if (looking-at "#![ \t]*\\([^\n]*\\)$")
            (and (goto-char (match-beginning 1))
                 ;; If the line ends in a space,
                 ;; don't offer to change it.
@@ -247,8 +248,13 @@ executable-set-magic
                                      "Replace magic number by `#!%s'? "
                                      argument))))
                     (progn
-                      (replace-match argument t t nil 1)
-                      (message "Magic number changed to `#!%s'" 
argument))))
+                       ;; Repeat search to work around match-data loss
+                       ;; from call to `save-window-excursion' above.
+                       (goto-char (point-min))
+                       (if (looking-at "^#![ \t]*\\([^\n]*\\)$")
+                           (progn
+                            (replace-match argument t t nil 1)
+                            (message "Magic number changed to `#!%s'" 
argument))))))
          (insert "#!" argument ?\n)
          (message "Magic number changed to `#!%s'" argument))))
     interpreter)
-- 

Message #8 received at 54218 <at> debbugs.gnu.org (full text, mbox):

From: Andreas Schwab <schwab <at> linux-m68k.org>
To: "Andrew L. Moore" <slewsys <at> gmail.com>
Cc: 54218 <at> debbugs.gnu.org
Subject: Re: bug#54218: [PATCH] Magic number regexp shouldn't match beyond
 end-of-line.
Date: Wed, 02 Mar 2022 09:23:55 +0100

On Mär 01 2022, Andrew L. Moore wrote:

> diff --git a/lisp/progmodes/executable.el b/lisp/progmodes/executable.el
> index d7c093444e..9116bdea9d 100644
> --- a/lisp/progmodes/executable.el
> +++ b/lisp/progmodes/executable.el
> @@ -232,7 +232,8 @@ executable-set-magic
>         (save-excursion
>          (goto-char (point-min))
>          (add-hook 'after-save-hook 'executable-chmod nil t)
> -       (if (looking-at "#![ \t]*\\(.*\\)$")
> +        ;; Regexp shouldn't match beyond end-of-line.
> +       (if (looking-at "#![ \t]*\\([^\n]*\\)$")

In Emacs regexps, `.' doesn't match newlines.

-- 
Andreas Schwab, schwab <at> linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Message #11 received at 54218 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Andrew L. Moore" <slewsys <at> gmail.com>
Cc: 54218 <at> debbugs.gnu.org
Subject: Re: bug#54218: [PATCH] Magic number regexp shouldn't match beyond
 end-of-line.
Date: Thu, 03 Mar 2022 15:42:43 +0100

"Andrew L. Moore" <slewsys <at> gmail.com> writes:

> Repeat magic number search to work around match-data loss
> when `save-window-excursion' is called.

I think it would perhaps make more sense to just save the match data
instead of repeating the match, so I've now done so in Emacs 29

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #16 received at 54218 <at> debbugs.gnu.org (full text, mbox):

From: "Andrew L. Moore" <slewsys <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 54218 <at> debbugs.gnu.org
Subject: Re: bug#54218: [PATCH] Magic number regexp shouldn't match beyond
 end-of-line.
Date: Thu, 3 Mar 2022 14:57:06 -0500

On 3/3/22 09:42, Lars Ingebrigtsen wrote:
> "Andrew L. Moore" <slewsys <at> gmail.com> writes:
> 
>> Repeat magic number search to work around match-data loss
>> when `save-window-excursion' is called.
> 
> I think it would perhaps make more sense to just save the match data
> instead of repeating the match, so I've now done so in Emacs 29

Yes, this resolves the issues that I was seeing.

For the record, I'm not able to reproduce the data loss with
vanilla Emacs by calling `executable-set-magic' manually.  It
occurs (for me) when `executable-set-magic' is called automatically
from a minor mode.  In any case, your patch fixes my minor mode
and does no harm.

The other issue that I attributed to the regexp matching beyond
EOL was caused by `replace-match' being called by incorrect or
uninitialized match data.  Your patch resolves this as well.
Thank you!

Message #19 received at 54218 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Andrew L. Moore" <slewsys <at> gmail.com>
Cc: 54218 <at> debbugs.gnu.org
Subject: Re: bug#54218: [PATCH] Magic number regexp shouldn't match beyond
 end-of-line.
Date: Fri, 04 Mar 2022 16:37:43 +0100

"Andrew L. Moore" <slewsys <at> gmail.com> writes:

> The other issue that I attributed to the regexp matching beyond
> EOL was caused by `replace-match' being called by incorrect or
> uninitialized match data.  Your patch resolves this as well.

Thanks for checking.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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