From: Troy Hinckley <troyhinckley@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: question about Qnil representation
Date: Wed, 26 Oct 2022 10:04:47 -0600 [thread overview]
Message-ID: <5d85a71f-500e-43c7-a1fb-47ffe8518d94@Spark> (raw)
In-Reply-To: <8335bao9rs.fsf@gnu.org>
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Sure, but it reinterprets the integer as a *Lisp_Symbol to get at the actual struct correct? Or am I misunderstanding how this works?
On Oct 26, 2022, 10:00 AM -0600, Eli Zaretskii <eliz@gnu.org>, wrote:
> > Date: Wed, 26 Oct 2022 09:40:30 -0600
> > From: Troy Hinckley <troyhinckley@gmail.com>
> >
> > I have been reading through the C source to try and learn it and understand it better. I saw in Changeling.13 an
> > entry From Paul Eggert on 2015-01-05 with “Use 0 for Qnil” As a fix for Bug#15880. How does this work in
> > practice? It looks like symbols are just pointers, but 0 would not be a valid pointer. I don’t see any special code
> > for handling the null case.
>
> Symbols are not pointers, they have the same C type as any other
> Lisp_Object. If Lisp_Object is represented by an integer number, then
> zero is a valid integer number as well.
>
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next prev parent reply other threads:[~2022-10-26 16:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5a560265-fa81-42d2-945b-ab85d72df9e6@Spark>
2022-10-26 15:40 ` question about Qnil representation Troy Hinckley
2022-10-26 16:00 ` Eli Zaretskii
2022-10-26 16:04 ` Troy Hinckley [this message]
2022-10-26 16:09 ` Eli Zaretskii
2022-10-27 0:45 ` Po Lu
2022-10-26 16:16 ` Matt Armstrong
2022-10-26 16:22 ` Troy Hinckley
2022-10-26 16:45 ` Eli Zaretskii
2022-10-26 18:46 ` Troy Hinckley
2022-10-26 19:01 ` Stefan Monnier
2022-10-26 19:03 ` Eli Zaretskii
2022-10-27 0:47 ` Po Lu
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