Re: [Emacs-diffs] master 8ba156f: Attempt to avoid crashes in plist-member

[David Kastrup]

Eli Zaretskii <address@hidden> writes:

>> Cc: address@hidden
>> From: Paul Eggert <address@hidden>
>> Date: Mon, 12 Oct 2015 20:36:06 -0700
>> 
>>     QUIT could call some Lisp.
>>
>> Sure, but Lisp cannot affect the value of CONSP (plist).
>
> Not the value of CONSP, the list itself.  We follow the CONSP test
> with XCAR, which crashed.  The only way I could imagine that happening
> is that the list got modified between the test and the XCAR call.  Is
> there any other way to explain that?

Huh?  CONSP only checks some bits on a pointer.  It does not verify that
the pointer can be dereferenced into an existing cons cell.  So there is
absolutely no need to modify anything between having a true CONSP test
and a crashing XCAR.

-- 
David Kastrup