From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: thoughts on reallocarray, explicit_bzero?
Date: Mon, 19 May 2014 12:55:23 -0400 [thread overview]
Message-ID: <20140519165523.GP507@brightrain.aerifal.cx> (raw)
In-Reply-To: <20140519162556.GY12324@port70.net>
On Mon, May 19, 2014 at 06:25:57PM +0200, Szabolcs Nagy wrote:
> i'd use a saturated multiplication, because malloc/realloc
> are not the only places where overflowing size calculations
> may cause problems and in such cases (size_t)-1 is just as
> good as a failure and it can be added to your code without
> portability issues
>
> static size_t sizemul(size_t a, size_t b)
> {
> return b>1 && a>1 && a>-1/b ? -1 : a*b;
> }
On 32-bit this can easily be optimized to just one conditional instead
of three:
uint64_t tmp = (uint64_t)a * b;
return tmp>SIZE_MAX ? SIZE_MAX : tmp;
Of course that requires an ifdef, which is perhaps ugly.
Rich
next prev parent reply other threads:[~2014-05-19 16:55 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-19 15:31 Isaac Dunham
2014-05-19 15:43 ` Rich Felker
2014-05-19 16:19 ` Daniel Cegiełka
2014-05-20 6:19 ` Rich Felker
2014-05-20 15:50 ` Daniel Cegiełka
2014-05-19 15:44 ` Daniel Cegiełka
2014-05-19 16:16 ` Rich Felker
2014-05-19 16:30 ` Daniel Cegiełka
2014-05-19 16:32 ` Szabolcs Nagy
2015-01-28 22:01 ` Daniel Cegiełka
2015-01-28 22:34 ` Daniel Cegiełka
2015-01-28 22:38 ` Nathan McSween
2015-01-28 22:54 ` Daniel Cegiełka
2015-01-28 23:02 ` Josiah Worcester
2015-01-29 2:19 ` Rich Felker
2015-01-29 4:03 ` Brent Cook
2015-01-29 4:15 ` Rich Felker
2015-01-29 9:30 ` Daniel Cegiełka
2015-01-29 10:04 ` Szabolcs Nagy
2015-01-29 10:31 ` Daniel Cegiełka
2015-01-29 10:54 ` Daniel Cegiełka
2014-05-19 16:25 ` Szabolcs Nagy
2014-05-19 16:45 ` Daniel Cegiełka
2014-05-19 16:58 ` Rich Felker
2014-05-19 16:55 ` Rich Felker [this message]
2014-05-19 18:12 ` Szabolcs Nagy
2014-05-19 22:08 ` Andy Lutomirski
2014-05-20 0:41 ` Szabolcs Nagy
2014-06-11 9:59 ` Thorsten Glaser
2014-06-11 12:59 ` Rich Felker
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