bug#58338: 29.0.50; mapatoms called on more elements than in obarray?

[Eli Zaretskii]

> From: Philip Kaludercic <philipk@posteo.net>
> Date: Thu, 06 Oct 2022 16:16:03 +0000
> 
> 
> >From reading the docstring of `mapatoms', I would assume that this would
> evaluate to t:
> 
> (let ((i 0))
>   (mapatoms (lambda (_) (setq i (1+ i))) obarray)
>   (= (length obarray) i))
> 
> But instead on my system I get (length obarray) ↝ 15121 and and i ↝
> 78050, which is are at a ratio of 5.16169565505.
> 
> Also interesting, if I intern a variable "foo", the value of i increases
> to 83106, while (length obarray) stays the same (?)

You assume that obarray is a flat vector or something?  Or how about
if you explain why the above surprised you?