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

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Message #44 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: bug-gnu-emacs <at> gnu.org, Nicolas Petton <nicolas <at> petton.fr>,
 30626 <at> debbugs.gnu.org
Subject: Re: bug#30626: 26.0.91;
 Crash when traversing a `stream-of-directory-files'
Date: Wed, 28 Feb 2018 12:05:09 +0100

Hello,

I had written that

> > (seq-doseq (_ (stream-range 1 1000000)) nil)

crashes.  CC'ing Nicolas, the author of stream.el.

> What can we do instead in such cases?  Stack-overflow protection
> cannot work in GC, so you are shooting yourself in the foot by
> creating such large recursive structures.  By the time we get to GC,
> where the problem will happen, it's too late, because the memory was
> already allocated.
>
> Does anyone has a reasonable idea for avoiding the crash in such
> programs?

I would appreciate any effort to fix that, because it seems that
currently streams are broken by design, and there is no way to fix that
from the Lisp implementation.

Yes, we could implement iterators instead of streams - that's what we
get when we avoid the consing.  But it's something different and not
always an alternative, depending on what you want to do.


Michael.

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