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bug#54501: Segfault on recursive structure
From: |
Andreas Schwab |
Subject: |
bug#54501: Segfault on recursive structure |
Date: |
Tue, 22 Mar 2022 16:02:57 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.92 (gnu/linux) |
On Mär 22 2022, Lars Ingebrigtsen wrote:
> So this bug report is about two things. The first is that this reads to
> (nil):
>
> #0=#0#
>
> Which seems odd. Reading #0=#1# signals an error, but it's not
> immediately clear to me whether #0=#0# is totally nonsensical or not.
> And if not, is (nil) the right result? Anybody?
That's an side effect of the implementation: (nil) is the placeholder
object which #0# then references.
> The other thing is more serious, and reading the following will segfault
> your Emacs, so don't do that:
>
> #0=[#1=(#0# . #1#)]
>
> Now, Emacs segfaults on trying to gc a number of recursive objects
> (especially ones that recurse in the `car'), but this seems to actually
> segfault in the reader. Is it obvious to anybody why?
Does it crash in substitute_object_recurse?
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
bug#54501: Segfault on recursive structure, Mattias Engdegård, 2022/03/26