From: Daniel Colascione <dancol@dancol.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org
Subject: Re: Conservative GC isn't safe
Date: Mon, 28 Nov 2016 10:03:49 -0800 [thread overview]
Message-ID: <f336a0a2-fcb2-fd12-4195-51a3dd5bc910@dancol.org> (raw)
In-Reply-To: <838ts3zdpk.fsf@gnu.org>
On 11/28/2016 10:00 AM, Eli Zaretskii wrote:
>> From: Daniel Colascione <dancol@dancol.org>
>> Date: Mon, 28 Nov 2016 09:51:37 -0800
>>
>> struct foo* f = something();
>> int* x = f->&field;
>> something_else(); // invalidate global memory
>> *x = 5; // f is dead here, but still in scope
>>
>> Even if you don't write this kind of code, the compiler is allowed to
>> generate it.
>
> But there's no such code in Emacs, and will never be.
I think you have too little faith in the ingenuity of compiler writers.
Why can't the compiler generate this sort of code in cases we don't
anticipate?
> Lisp objects we
> create are either temporaries that can be GC'ed, or values that cannot
> be GC'ed, in which case they are passed to some other code, either a
> callee or returned as a value. The only ones that can be dead as
> above are the first variety, about which we don't care.
When this assumption stops holding, it's going to be very difficult to
debug the resulting occasional crashes. Wouldn't it be easier to use the
information *already in the memory tree* to make GC more conservative
and understand interior pointers?
next prev parent reply other threads:[~2016-11-28 18:03 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
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 [this message]
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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