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From: Paul Eggert <eggert@cs.ucla.edu>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: Opportunistic garbage collection
Date: Thu, 25 Apr 2019 15:14:16 -0700	[thread overview]
Message-ID: <ffa3ed50-fc82-0c9a-29c3-e71a48f04385@cs.ucla.edu> (raw)
In-Reply-To: <jwvbm0uvtwi.fsf-monnier+emacs@gnu.org>

On 4/25/19 11:18 AM, Stefan Monnier wrote:
>
>> This assumes byte_ct is not narrower than EMACS_INT, which isn't true on
>> 32-bit platforms --with-wide-int.
> Does it?  My understanding is that if byte_ct is narrower what happens
> is:
>
> 1- consing_since_gc is widened to EMACS_INT, preserving the mathematical value.
> 2- multiplication with `fact`.

And since that's signed integer multiplication, it can overflow with
undefined behavior.




  reply	other threads:[~2019-04-25 22:14 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-24 20:54 Opportunistic garbage collection Stefan Monnier
2019-04-25  0:17 ` Paul Eggert
2019-04-25  6:27   ` Eli Zaretskii
2019-04-25 12:49     ` Stefan Monnier
2019-04-25 18:18   ` Stefan Monnier
2019-04-25 22:14     ` Paul Eggert [this message]
2019-04-26  0:15       ` Stefan Monnier

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