Date: Fri, 27 May 2005 11:26:27 -0400 From: John Baldwin <jhb@FreeBSD.org> To: freebsd-amd64@FreeBSD.org, Adriaan de Groot <groot@kde.org> Subject: Re: amd64/81279: /usr/games/random returns every line Message-ID: <200505271126.28696.jhb@FreeBSD.org> In-Reply-To: <200505192130.j4JLU7wg078285@freefall.freebsd.org> References: <200505192130.j4JLU7wg078285@freefall.freebsd.org>
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On Thursday 19 May 2005 05:30 pm, Adriaan de Groot wrote:
> The following reply was made to PR amd64/81279; it has been noted by GNATS.
>
> From: Adriaan de Groot <groot@kde.org>
> To: bug-followup@freebsd.org, vivek@khera.org
> Cc:
> Subject: Re: amd64/81279: /usr/games/random returns every line
> Date: Thu, 19 May 2005 23:26:08 +0200
>
> Problem is lines like
>
> selected = (int)(denom * random() / LONG_MAX) == 0;
>
> which cause the overflow. Replacing LONG_MAX with INT_MAX here fixes the
> bug. (The same replacement should probably be done in the other two places
> that LONG_MAX occurs, since the -e flag is similarly broken.)
I can't see how the overflow happens. Oh. From the manpage:
DESCRIPTION
The random() function uses a non-linear additive feedback random number
generator employing a default table of size 31 long integers to return
successive pseudo-random numbers in the range from 0 to (2**31)-1. The
period of this random number generator is very large, approximately
16*((2**31)-1).
So I guess the real fix is to replace LONG_MAX with RAND_MAX?
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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