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From: Alejandro Colomar <alx.manpages@gmail.com>
To: Jonny Grant <jg@jguk.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>,
	linux-man <linux-man@vger.kernel.org>,
	GNU C Library <libc-alpha@sourceware.org>,
	Florian Weimer <fweimer@redhat.com>
Subject: Re: [PATCH] Add example to rand.3
Date: Wed, 28 Dec 2022 21:56:47 +0100	[thread overview]
Message-ID: <b2ee2571-952e-4709-314d-ec4952a44ed8@gmail.com> (raw)
In-Reply-To: <da69ac41-1ea0-b852-4e9a-3d27a10f2bd7@jguk.org>


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Hi Jonny,

On 12/28/22 21:51, Jonny Grant wrote:
> You're completely right. It's a real issue if software starts multiple times per second, or executes in less than one second and then runs again. Our software always runs for at least minutes, maybe another code suggestion for a seed would be good instead, like arc4random. I do like that rand() offers a reproducible sequence, useful when in some other software we logged the seed value used. random.4 - /dev/random would be a better seed than time(NULL) if running the program multiple times per second. Anyway, rand() is only pseudo-random, utilising /dev/random would be really much more random, and I like that the seed is saved between reboots.

Ahh, I didn't connect the dots the other day!  We don't need to wait for glibc. 
libbsd already provides arc4random on GNU/Linux systems, so I can already 
recommend using arc4random to seed srand(3).

I'll prepare a patch...

Cheers,

Alex

> 
> Cheers, Jonny
> 

-- 
<http://www.alejandro-colomar.es/>

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  reply	other threads:[~2022-12-28 20:57 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-26 21:50 [PATCH] Add example to rand.3 Jonny Grant
2022-12-26 22:29 ` Alejandro Colomar
2022-12-27 13:07   ` Cristian Rodríguez
2022-12-27 23:33     ` Alejandro Colomar
2022-12-28  0:00       ` G. Branden Robinson
2022-12-28  0:41         ` Alejandro Colomar
2022-12-28 12:21           ` Cristian Rodríguez
2022-12-30 18:15             ` Joseph Myers
2022-12-30 18:20               ` Alejandro Colomar
2022-12-30 18:50                 ` Joseph Myers
2022-12-30 18:58                   ` Alejandro Colomar
2022-12-30 19:11               ` Cristian Rodríguez
2022-12-30 21:08                 ` Joseph Myers
2022-12-30 21:15                   ` Internal organization of "the implementation" (was: [PATCH] Add example to rand.3) Alejandro Colomar
2022-12-30 21:50                     ` Joseph Myers
2022-12-27 21:37   ` [PATCH] Add example to rand.3 Jonny Grant
2022-12-27 23:11     ` Alejandro Colomar
2022-12-28 20:51       ` Jonny Grant
2022-12-28 20:56         ` Alejandro Colomar [this message]
2022-12-28 21:03           ` Alejandro Colomar
2022-12-28 21:04             ` Alejandro Colomar
2022-12-28 21:25               ` Jonny Grant
2022-12-28 21:32                 ` Alejandro Colomar
2022-12-28 21:04           ` Cristian Rodríguez
2022-12-28 21:11             ` Alejandro Colomar
2022-12-28 21:19               ` Jonny Grant
2022-12-28 21:18             ` Alejandro Colomar

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