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: Noam Postavsky <npostavs <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, Nicolas Petton <nicolas <at> petton.fr>, 30626 <at> debbugs.gnu.org
Subject: bug#30626: 26.0.91; Crash when traversing a `stream-of-directory-files'
Date: Thu, 25 Apr 2019 07:19:29 +0200

Noam Postavsky <npostavs <at> gmail.com> writes:

> Coming back to this again.  I think I got lost in the weeds of the
> byte-code function objects before.  The core problem is that streams
> are not exactly encoded like the above, because even after forcing it
> you don't have just a plain SECOND-VALUE stored in the stream.  The
> original FUNCTION-TO-PRODUCE-MORE-REST-OF-LIST stays around and keeps
> referencing all the code and all the following elements.  So a
> possible solution is change the stream to get rid of the lambda part
> and just leave the computed value after it's forced.  With the
> following patch (stream-flush (stream-range 1 1000000)) succeeds:
>
> [Patch...]

Works for me, and it makes sense.  As a test case I recompiled
el-search.el (it uses streams for several things) with your patch
applied to stream.el, and it worked well.

> Some additional things that I thought of changing, but I didn't yet:

> - stream--identifier vs just using '--stream-- directly, I don't see
>   what's the benefit of indirection here.

A matter of taste I guess.

> - stream-make should use cons instead of list (or maybe a struct?).

I think cons would be ok.  Would a struct make things slower?

> - stream-empty should just be a constant.

Dunno if there are cases where this would be problematic, but I guess we
could do this as well.

Anyway, thanks for looking into this again, I like your solution.  Maybe
Nicolas can also chime in.


Michael.

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