Subject: bug#63722: closed (Re: bug#63722: 29.0.91; (elisp) Skip to end #@00 does not work)

From: [email-masked] (GNU bug Tracking System)
Date: Fri, 26 May 2023 09:23:02 +0000

Your bug report

#63722: 29.0.91; (elisp) Skip to end #@00 does not work

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
63722: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=63722
GNU Bug Tracking System
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Subject: Re: bug#63722: 29.0.91; (elisp) Skip to end #@00 does not work
From: Mattias Engdegård <[email-masked]>
To: Eli Zaretskii <[email-masked]>
Cc: [email-masked], richard newton <[email-masked]>
Date: Fri, 26 May 2023 11:22:40 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

25 maj 2023 kl. 20.44 skrev Eli Zaretskii <[email-masked]>:

>> With emacs 29.0.91 pretest, the "skip to end" syntax #@00 no longer seems to work. For example,
>> with the three lines below in a buffer (eval-buffer) gives the error - End of file during parsing. With
>> previous emacs versions it did not complain.
>> 
>> (setq testStr "zz")
>> #@00
>> should be ignored

Thank you for reporting this. The undocumented #@00 behaviour has indeed been co-opted by parts of the community as an 'pretend end-of-file occurs here' mechanism, but it actually works as if only the value `nil` were left in the buffer. This is fine in files containing Lisp source where a top-level nil has no effect, but could cause trouble if used in Lisp data files.

Obviously we are going to keep the old reader behaviour for compatibility for now since there is little to gain from not doing so.

Ideally we should stop handling comments and whitespace in readevalloop because the actual reader (read0) is perfectly capable of doing that. We need a way to distinguish 'EOF before anything could be read' from 'EOF when we have read an incomplete value', both of which currently signal `end-of-file`. Not sure how best to do that in a compatible way, however.

> Does the below look like the correct way of fixing this regression?

Thank you and yes, roughly speaking -- a fix has now been pushed to emacs-29, and I'm closing the bug.

Subject: 29.0.91; (elisp) Skip to end #@00 does not work
From: richard newton <[email-masked]>
To: [email-masked]
Date: Thu, 25 May 2023 16:19:42 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

With emacs 29.0.91 pretest, the "skip to end" syntax #@00 no longer seems
to work. For example, with the three lines below in a buffer (eval-buffer)
gives the error - End of file during parsing. With previous emacs versions
it did not complain.

(setq testStr "zz")
#@00
should be ignored

In GNU Emacs 29.0.91 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.37, cairo version 1.16.0) of 2023-05-18 built on n26-hp
Windowing system distributor 'The X.Org Foundation', version 11.0.12201009
System Description: Debian GNU/Linux 12 (bookworm)

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB