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From: Troy Hinckley <troyhinckley@gmail.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org, matt@rfc20.org
Subject: Re: question about Qnil representation
Date: Wed, 26 Oct 2022 12:46:39 -0600	[thread overview]
Message-ID: <168eb4b5-40be-43dc-8501-dc9f4c65c56f@Spark> (raw)
In-Reply-To: <83wn8mmt49.fsf@gnu.org>

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Ah, thank you. So it is not a pointer but an index. Is lispsym array resizable or is there a static limit to the number of symbols?
On Oct 26, 2022, 10:45 AM -0600, Eli Zaretskii <eliz@gnu.org>, wrote:
> > Date: Wed, 26 Oct 2022 10:22:54 -0600
> > From: Troy Hinckley <troyhinckley@gmail.com>
> >
> > Let me try again. As I understand it, every Symbol is an instance if Lisp_Symbol. The Lisp_Object is an
> > integer that can represent multiple types with tags defined by Lisp_Type. If the tag is 0, then the type is a
> > symbol. In that case you would treat the rest of the bytes in the Lisp_Object as pointer to a Lisp_Symbol
> > instance. However if the symbol nil is defined as 0, then it is not a pointer to anything. How then do you access
> > that symbol? Is there special case code to handle the null pointer?
>
> See make_lisp_symbol and builtin_lisp_symbol, and I think you will
> understand what's going on here. Also see the value stored in
> lispsym[0].
>

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  reply	other threads:[~2022-10-26 18:46 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
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 [this message]
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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