From: Szabolcs Nagy <nsz@port70.net>
To: musl@lists.openwall.com
Subject: Re: thoughts on reallocarray, explicit_bzero?
Date: Mon, 19 May 2014 20:12:58 +0200 [thread overview]
Message-ID: <20140519181257.GA12324@port70.net> (raw)
In-Reply-To: <20140519165523.GP507@brightrain.aerifal.cx>
* Rich Felker <dalias@libc.org> [2014-05-19 12:55:23 -0400]:
> On Mon, May 19, 2014 at 06:25:57PM +0200, Szabolcs Nagy wrote:
> > 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.
or without ifdef
static size_t sizemul(size_t a, size_t b)
{
if (2*sizeof a <= sizeof 1ULL) {
unsigned long long m = 1ULL*a*b;
return m>>8*sizeof a ? -1 : m;
}
return (a|b)>>4*sizeof a && b && a>-1/b ? -1 : a*b;
}
next prev parent reply other threads:[~2014-05-19 18:12 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
2014-05-19 18:12 ` Szabolcs Nagy [this message]
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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