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

From: Alan Mackenzie <[email-masked]>
Date: Mon, 7 Aug 2023 09:20:25 +0000

Hello, Stefan.

On Sun, Aug 06, 2023 at 23:30:15 -0400, Stefan Monnier wrote:
> > at the top level of the function.  Thus

> >     (equal 'foo #<symbol foo at 42>)

> > will return non-nil, regardless of the setting of
> > `symbols-with-pos-enabled`.  It should return non-nil only when that
> > flag variable is non-nil.  This is a bug.

> Could you explain why you think it's a bug?

When symbols-with-pos-enabled is non-nil, the two arguments to that
equal call are equal.  That is the point of s-w-p-e.

When s-w-p-e is nil, and the "magic" is thus switched off, the two lisp
objects have different type (the first is a symbol, the second is a
pseudovector), thus cannot be equal.

I think the amendments I've proposed for the elisp manual page "Symbols
with Position" are now clearer about this sort of thing.

>         Stefan

-- 
Alan Mackenzie (Nuremberg, Germany).