From: Paul Eggert <eggert@cs.ucla.edu>
To: Eli Zaretskii <eliz@gnu.org>, Noam Postavsky <npostavs@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Strange code in emacs.c
Date: Wed, 3 Oct 2018 10:36:35 -0700 [thread overview]
Message-ID: <28cf3cf7-8be2-9f6b-711d-bfbd2b625936@cs.ucla.edu> (raw)
In-Reply-To: <83h8i32ha8.fsf@gnu.org>
Eli Zaretskii wrote:
> We have this in 'main':
>
> emacs_re_safe_alloca = max
> (min (lim - extra, SIZE_MAX) * (min_ratio / ratio),
> MAX_ALLOCA);
>
> This always yields MAX_ALLOCA because 'ratio' is always greater than
> 'min_ratio':
>
> int min_ratio = 20 * sizeof (char *);
> int ratio = min_ratio + min_ratio / 3;
>
> Don't we mean to set emacs_re_safe_alloca like this instead:
>
> emacs_re_safe_alloca = min (lim - extra, SIZE_MAX) / ratio;
> emacs_re_safe_alloca = max (emacs_re_safe_alloca * min_ratio, MAX_ALLOCA);
Yes, that sounds better to me too. Also, that SIZE_MAX should be changed to min
(SIZE_MAX, PTRDIFF_MAX) to avoid (unlikely) integer-overflow issues.
Should this fix be put into master or into the emacs-26 branch?
next prev parent reply other threads:[~2018-10-03 17:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-03 15:15 Strange code in emacs.c Eli Zaretskii
2018-10-03 17:36 ` Paul Eggert [this message]
2018-10-03 17:42 ` Eli Zaretskii
2018-10-03 18:29 ` Paul Eggert
2018-10-03 22:12 ` Noam Postavsky
2018-10-03 22:59 ` Paul Eggert
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