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From: Lars Ingebrigtsen <larsi@gnus.org>
To: Andy Moreton <andrewjmoreton@gmail.com>
Cc: 32605@debbugs.gnu.org
Subject: bug#32605: [w64] (random) never returns negative
Date: Thu, 12 Aug 2021 15:17:46 +0200	[thread overview]
Message-ID: <87mtpmls3p.fsf_-_@gnus.org> (raw)
In-Reply-To: <vz1k1o05bdb.fsf@gmail.com> (Andy Moreton's message of "Wed, 05 Sep 2018 14:20:48 +0100")

Andy Moreton <andrewjmoreton@gmail.com> writes:

>> This bug seems specific to 64 bit Windows builds.
>
> ON 64bit Windows, sysdep.c sets RAND_BITS to 31, but random (in w32.c)
> only provides 30 bits. It looks like the mixing in get_random does not
> result in the top fixnum bit being set.

So it's this:

int
random (void)
{
  /* rand_as183 () gives us 15 random bits...hack together 30 bits.  */
  return ((rand_as183 () << 15) | rand_as183 ());
}

So running rand_as183 and taking another bit from that might do the
trick?  Eli, do you have any comments here?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no





  reply	other threads:[~2021-08-12 13:17 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-01 17:18 bug#32605: 26.1; (random) never returns negative Francis Wright
2018-09-01 17:34 ` Stephen Berman
2018-09-04 22:27   ` Noam Postavsky
2018-09-05 13:20     ` Andy Moreton
2021-08-12 13:17       ` Lars Ingebrigtsen [this message]
2021-08-12 13:42         ` bug#32605: [w64] " Eli Zaretskii
2021-08-12 20:34           ` Andy Moreton
2021-08-13  6:29             ` Eli Zaretskii
2021-08-13 21:12               ` Andy Moreton
2021-08-14  5:54                 ` Eli Zaretskii
2021-08-14  8:31                   ` Andy Moreton
2021-08-14  8:57                     ` Eli Zaretskii
2021-08-14 11:06                       ` Andy Moreton
2021-08-14 11:33                         ` Eli Zaretskii
2021-08-14 12:10                           ` Andy Moreton
2021-08-14 12:36                             ` Eli Zaretskii
2021-08-14 13:40                               ` Andy Moreton
2021-08-14 14:43                                 ` Eli Zaretskii
2021-08-14 18:47                                   ` Andy Moreton
2021-08-15  6:07                                     ` Eli Zaretskii

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