GNU bug report logs - #30626
26.0.91; Crash when traversing a `stream-of-directory-files'

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From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: npostavs <at> gmail.com, 30626 <at> debbugs.gnu.org
Subject: bug#30626: 26.0.91; Crash when traversing a `stream-of-directory-files'
Date: Wed, 28 Feb 2018 17:20:53 +0100

Eli Zaretskii <eliz <at> gnu.org> writes:

> How do you see that the car is immediately thrown away?

After expansion and dispatch, this is what gets executed:

#+begin_src emacs-lisp
(let ((stream (stream-range 1 1000000)))
  (while (not (stream-empty-p stream))
    (funcall #'ignore (stream-first stream))
    (setq stream (stream-rest stream))))
#+end_src

Creating an element and throwing away the outermost cons alternate.

> > AFAIU the problem is that the cons1 still exists in memory until
> > garbage collection kicks in.  When that happens, the cons1 points to
> > a largely recursive cons structure, though this structure is never
> > referenced from Lisp in this form.

> What is "cons1" in this context?

I said it some lines above: I defined it as name of the "first cons",
i.e. the original stream.  The return value of `stream-range' in the
above example.


Michael.

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