From: Paul Eggert <eggert@cs.ucla.edu>
To: Daniel Colascione <dancol@dancol.org>,
Emacs developers <emacs-devel@gnu.org>
Subject: Re: Conservative GC isn't safe
Date: Sat, 26 Nov 2016 00:30:21 -0800 [thread overview]
Message-ID: <66485157-00cd-4704-a421-cbfe84299cae@cs.ucla.edu> (raw)
In-Reply-To: <fd2714c0-b9f7-bde8-cac2-8e4f317a346a@dancol.org>
On 11/26/2016 12:11 AM, Daniel Colascione wrote:
>
> 1) mark_maybe_pointer looks only for exact matches on object start.
> It's perfectly legal for the compiler to keep an interior object
> pointer and discard the pointer to the object start.
Yes, just as it's perfectly legal for the compiler to subtract 42 from
every pointer before putting it in a register or storing it into memory.
In practice, though, compilers don't do this around calls to the garbage
collector. (True, this assumption should be documented better.)
>
> 2) INTERVAL is GCed, but it's not represented in the memory tree:
> struct interval isn't a real lisp object and it's allocated as
> MEM_TYPE_NON_LISP. Even a direct pointer to the start of an interval
> won't protect it from GC. Shouldn't we treat intervals like conses?
Does the code ever create an interval that is accessible only via locals
when a GC occurs? If not, Emacs should be OK. (This should also be
documented better.)
next prev parent reply other threads:[~2016-11-26 8:30 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-26 8:11 Conservative GC isn't safe Daniel Colascione
2016-11-26 8:30 ` Paul Eggert [this message]
2016-11-26 8:33 ` Daniel Colascione
2016-11-26 9:01 ` Eli Zaretskii
2016-11-26 9:04 ` Daniel Colascione
2016-11-26 9:24 ` Eli Zaretskii
2016-11-26 15:05 ` Stefan Monnier
2016-11-26 15:21 ` Camm Maguire
2016-11-28 17:51 ` Daniel Colascione
2016-11-28 18:00 ` Eli Zaretskii
2016-11-28 18:03 ` Daniel Colascione
2016-11-28 18:50 ` Eli Zaretskii
2016-11-28 18:03 ` Stefan Monnier
2016-11-28 19:18 ` Daniel Colascione
2016-11-28 19:33 ` Stefan Monnier
2016-11-28 19:37 ` Eli Zaretskii
2016-11-28 19:40 ` Daniel Colascione
2016-11-28 20:03 ` Eli Zaretskii
2016-11-28 20:09 ` Daniel Colascione
2016-11-28 19:26 ` Andreas Schwab
2016-11-28 19:34 ` Stefan Monnier
2016-11-26 15:03 ` Stefan Monnier
2016-11-26 15:12 ` Eli Zaretskii
2016-11-26 16:29 ` Stefan Monnier
2016-11-26 16:42 ` Eli Zaretskii
2016-11-26 18:43 ` Stefan Monnier
2016-11-27 6:17 ` Ken Raeburn
2016-11-27 15:39 ` Eli Zaretskii
2016-11-28 9:50 ` Ken Raeburn
2016-11-28 15:55 ` Eli Zaretskii
2016-11-27 16:15 ` Paul Eggert
2016-11-28 9:36 ` Ken Raeburn
2016-11-28 15:55 ` Eli Zaretskii
2016-11-28 16:15 ` Stefan Monnier
2016-11-28 17:37 ` Eli Zaretskii
2016-11-28 17:49 ` Stefan Monnier
2016-11-28 17:57 ` Eli Zaretskii
2016-11-28 18:05 ` Stefan Monnier
2016-11-28 19:09 ` Ken Raeburn
2016-11-28 19:33 ` Eli Zaretskii
2016-11-29 8:49 ` Ken Raeburn
2016-11-28 17:03 ` Björn Lindqvist
2016-11-28 16:13 ` Paul Eggert
2016-11-27 16:52 ` Stefan Monnier
2016-11-26 19:08 ` Pip Cet
2016-11-27 0:24 ` Paul Eggert
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