unofficial mirror of emacs-devel@gnu.org 
 help / color / mirror / code / Atom feed
From: "Gerd Möllmann" <gerd.moellmann@gmail.com>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
Subject: Re: Question regarding Lisp_Object representation of symbols
Date: Thu, 07 Mar 2024 05:28:03 +0100	[thread overview]
Message-ID: <m28r2uzmwc.fsf@Pro.fritz.box> (raw)
In-Reply-To: <b8345f3d-a227-475b-be35-ad3c4e46e3f3@cs.ucla.edu> (Paul Eggert's message of "Wed, 6 Mar 2024 12:32:35 -0800")

Paul Eggert <eggert@cs.ucla.edu> writes:

> On 2024-03-06 04:14, Eli Zaretskii wrote:
>>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>>>
>>> - Does someone remember the reasons why this has been done?
>
> Speed. It's significantly more efficient.
>
>>> - Is there something that relies on this? Maybe something that
>>>    relies on 0x0 being a valid Lisp_Object?
>
> Yes, these assumptions are present in other places. I tried to mark
> all these places with "verify (NIL_IS_ZERO)" a decade ago, though I
> wouldn't be surprised if I missed one or two at the time, or if other
> dependencies have crept in since then (notably in src/comp.c, which I
> haven't audited for this).

Thanks, Paul. I've also looked around a bit yesterday, and my impression
in the end was that making !NIL_IS_ZERO fly could easily be more work
than trying to somehow marry it with the library I'm evaluating.



      reply	other threads:[~2024-03-07  4:28 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-06  6:48 Question regarding Lisp_Object representation of symbols Gerd Möllmann
2024-03-06  8:41 ` Po Lu
2024-03-06  8:56   ` Gerd Möllmann
2024-03-06 12:14 ` Eli Zaretskii
2024-03-06 20:32   ` Paul Eggert
2024-03-07  4:28     ` Gerd Möllmann [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://www.gnu.org/software/emacs/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=m28r2uzmwc.fsf@Pro.fritz.box \
    --to=gerd.moellmann@gmail.com \
    --cc=eggert@cs.ucla.edu \
    --cc=eliz@gnu.org \
    --cc=emacs-devel@gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/emacs.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).