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From: "Gerd Möllmann" <gerd.moellmann@gmail.com>
To: emacs-devel@gnu.org
Subject: Question regarding Lisp_Object representation of symbols
Date: Wed, 06 Mar 2024 07:48:31 +0100	[thread overview]
Message-ID: <m2ttljg8jk.fsf@Pro.fritz.box> (raw)

Symbols are currently encoded as words with tag = 0 (= Lisp_Symbol
enumerator), that when untagged are an offset from lispsym (the array of
built-in symbols), not a pointer to some structure like it is done for
other Lisp types. That makes the word 0x0 = Qnil, 0x1 = Qt, and so on.

My question comes from playing with another GC library, where this
unique encoding is, well, quite inconvenient. So, I'd like to ask two
questions:

- Does someone remember the reasons why this has been done?

- Is there something that relies on this? Maybe something that
  relies on 0x0 being a valid Lisp_Object?

Thanks!



             reply	other threads:[~2024-03-06  6:48 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-06  6:48 Gerd Möllmann [this message]
2024-03-06  8:41 ` Question regarding Lisp_Object representation of symbols 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

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