Subject: bug#65051: internal_equal manipulates symbols with position without checking symbols-with-pos-enabled.

From: Alan Mackenzie <[email-masked]>
Date: Sat, 5 Aug 2023 11:52:52 +0000

Hello, Eli.

On Sat, Aug 05, 2023 at 13:57:50 +0300, Eli Zaretskii wrote:
> > Date: Sat, 5 Aug 2023 10:45:37 +0000
> > Cc: [email-masked], [email-masked]
> > From: Alan Mackenzie <[email-masked]>

[ .... ]

> > > So we can have two different copies of #<symbol foo at 42>, such that
> > > their hex values are different?  Isn't that a bug? why don't we
> > > conflate such identical symbols?

> > No, it's not a bug, anymore than having two `equal' copies of '(a b c)
> > would be a bug.

> But with symbols we store them in obarray, and obarray ought to find
> the existing slot for #<symbol foo at 42> and reuse it, rather than
> create a new slot?

No, only the bare symbol is in the obarray.  The symbol with position
itself is a pseudovector, with contents (i) a bare symbol (a Lisp_Object
"pointing at" the obarray) and (ii) the unsigned integer position.

-- 
Alan Mackenzie (Nuremberg, Germany).