From: Eli Zaretskii <eliz@gnu.org>
To: Troy Hinckley <troyhinckley@gmail.com>
Cc: emacs-devel@gnu.org, matt@rfc20.org
Subject: Re: question about Qnil representation
Date: Wed, 26 Oct 2022 19:45:10 +0300 [thread overview]
Message-ID: <83wn8mmt49.fsf@gnu.org> (raw)
In-Reply-To: <d48212c3-9688-4a0a-8b1a-401b9ab43a2c@Spark> (message from Troy Hinckley on Wed, 26 Oct 2022 10:22:54 -0600)
> 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].
next prev parent reply other threads:[~2022-10-26 16:45 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 [this message]
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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