From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A462C433E0 for ; Fri, 5 Jun 2020 17:39:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE700206DB for ; Fri, 5 Jun 2020 17:39:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=gla.onmicrosoft.com header.i=@gla.onmicrosoft.com header.b="FByQ7a/Q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726044AbgFERjw (ORCPT ); Fri, 5 Jun 2020 13:39:52 -0400 Received: from hillend.cent.gla.ac.uk ([130.209.16.102]:63624 "EHLO hillend.cent.gla.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726788AbgFERjw (ORCPT ); Fri, 5 Jun 2020 13:39:52 -0400 X-Greylist: delayed 1000 seconds by postgrey-1.27 at vger.kernel.org; Fri, 05 Jun 2020 13:37:42 EDT Received: from cas08.campus.gla.ac.uk ([130.209.14.165]) by hillend.cent.gla.ac.uk with esmtp (Exim 4.72) (envelope-from ) id 1jhG1d-0003g5-7V; Fri, 05 Jun 2020 18:21:01 +0100 Received: from cas07.campus.gla.ac.uk (130.209.14.164) by cas08.campus.gla.ac.uk (130.209.14.165) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 5 Jun 2020 18:21:00 +0100 Received: from GBR01-CWL-obe.outbound.protection.outlook.com (104.47.20.59) by cas07.campus.gla.ac.uk (130.209.14.164) with Microsoft SMTP Server (TLS) id 15.0.1497.2 via Frontend Transport; Fri, 5 Jun 2020 18:21:00 +0100 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=OQcHYkfMNp/Tptv2l3Ci62xLkztmzjRvfk9xSAMuTLw/LhrvBpAJW8gIlRtkO53ha/CeJWLMuOKrtw7qzACTcpb5IMJc6GpztFioa5XCQKoSqmMpusjJhVBL8Eqg8whikIf/lqMJ0BaGQtxw8uNdDnBGHZ1BAu5thiGCdDEw5z+C59iSBZN4IFkXuezsbYtYbsg/xzJHMVLJ2jqX7ixHJldkgNDq3LXdi98FIkW/LDvG8HFLwAmBrLjbZSbT3P+HitKc0GHU3gkiLJBf8m1FhGRtYA33MRSPydWZIf85/YdZ4IgiLtBGaGiFs9rA5Tri/UcrHpmoU0rAF8f7wbSiTA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1W4k3lXT3Z6zxNcyB7ZAkVrVsmQ39w2maIaAHXnqc2Y=; b=QHVG+QpDXfq82RAbIWQLjGyUL7BAi2+k7Q4cGt8i6v7hkXLIaWOv/vKC32sng9KnQITRUKOAfHjr/kWF/pxw8rv++suNHVIvqcX750gI/F7ZW93iVNkfmPGOHub7P+ZHzOxG7VoiYbduLfdT7D9YDhfX6qTp03bvH2BAPAgGAfXclHSf+QpUizJBCiUsmhAMBQy6TpGJ1rbrEUy3dsURKe0f6SQuyEFuCqgqZ2TqVqJzsnipvBScGhm0u6MGM/U8Joz/s2TB6d5TqeIBt1IVSqmp8157s7Y3AGJyjwe3rdbIh6YCQ7k0IkuvFshul3amk5QWaVkw2sGIn8l8oKSmwA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=glasgow.ac.uk; dmarc=pass action=none header.from=glasgow.ac.uk; dkim=pass header.d=glasgow.ac.uk; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gla.onmicrosoft.com; s=selector2-gla-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1W4k3lXT3Z6zxNcyB7ZAkVrVsmQ39w2maIaAHXnqc2Y=; b=FByQ7a/Qysy0kAqaeDgyWGYsGi1I+Bs1eQzr+FrbEnPQD7ooNOlVox/HqBEpstkjH4WE5VTLBHraTA/B8l4tYB+RrncRS6NawqEvdSBtzrF5hFBugfJDDq6vAtJetnxc+JxHA7e8eUHC18T5kMEy7B6zTjvDECe9CO5Rl+V8ww4= Received: from LNXP265MB1001.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:84::12) by LNXP265MB0505.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:1b::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3066.20; Fri, 5 Jun 2020 17:21:00 +0000 Received: from LNXP265MB1001.GBRP265.PROD.OUTLOOK.COM ([fe80::edbd:dbdc:b744:15da]) by LNXP265MB1001.GBRP265.PROD.OUTLOOK.COM ([fe80::edbd:dbdc:b744:15da%7]) with mapi id 15.20.3045.024; Fri, 5 Jun 2020 17:21:00 +0000 From: John Marshall To: "mtk.manpages@gmail.com" CC: "linux-man@vger.kernel.org" Subject: random(3) and RAND_MAX Thread-Topic: random(3) and RAND_MAX Thread-Index: AQHWO12uQc3q+9KhbEeQvdYRDsPD3A== Date: Fri, 5 Jun 2020 17:21:00 +0000 Message-ID: <02185B3C-F6E5-4674-BB34-E549E04C5B37@glasgow.ac.uk> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=glasgow.ac.uk; x-originating-ip: [86.178.96.176] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 07bf366f-81c5-42e0-bc4e-08d80974d117 x-ms-traffictypediagnostic: LNXP265MB0505: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; x-forefront-prvs: 0425A67DEF x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: enfjYVFxE43stpyQ0gt51zYugCoo+zyCStNo2u7MOCZf7abkC0Fh0bp/UmAdV1jDKD7Cle+41SaipFZ4VYnZwcZrxRyGrneb1q8GBJOX5JdgsqnnHxZytOqg32f6jNXAPugqZVDGP83fcXUS/eSgiS4HUFO6D1dWHlkWIQj01r1XVUtfHZ2XrzGuGppIV1fQHemWXI6IZ/GZf/f2xHvshA4ZZBy7F6OaNzHTxkKyJ+QmFstvDlAW8Y7coFF0f/GAnFETGi7pOBSe6XKa6kPqtAoCScMrwLxpRhWgC9DWnfWsaiQucgvWM8Oy/r2qEeP7rYT7QtkUBZGjTmwiCPS4vw== x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LNXP265MB1001.GBRP265.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFTY:;SFS:(39860400002)(366004)(396003)(136003)(376002)(346002)(64756008)(83380400001)(478600001)(66556008)(6506007)(66446008)(66946007)(66476007)(316002)(2906002)(36756003)(6512007)(6486002)(26005)(786003)(5660300002)(71200400001)(76116006)(86362001)(2616005)(4326008)(8676002)(8936002)(33656002)(186003)(6916009);DIR:OUT;SFP:1101; x-ms-exchange-antispam-messagedata: d8gAlnce9dfRSx/4KxtEkwG9k+rplcqjtEB9EQAfpTo+1wUJLR7jJJZt7Ry/uA4abGY6rjvlOXb1gpQE8jYTnSH6BxvsZZCCeVRhOzxSyZ8PUNkiGJgdgMgBxeIS/W0YEf+Sc5qbchmoib2HUFqPGYd4X1ckLPVrSH5E/aEN2dSS6BTSE7CIKfHQ+tKFr8B91K3pK0TTln0Cf2CyOGXR38KhXiE7mMCIf01a94bYNsO+ou9LvMwPXBxpfMLqmAhtmj+ies58GX26zy+TnEUa92Wrz/MPFLKlvg0ZmQanUrnkN1bynOgbBte19HWlW9Lb83TWTDA5k9gnB8SduEHe5r6QpMcyNfcgLTYrfMLGMpNLQqltQYkHtr92jMifdT4L+YIUjnrW+zDG3pJYFCFOUGyy5fa6RZI8oWWmYwHhNR9WUNtN/VeyXCqsiVTI5w4iw71BZI7W9FHFiOA5X7OJqUgsR70hhq9ROYuRsM20BgE= x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-ID: <604B17EEEA6AAC46B17DE19BC1E0DAD7@GBRP265.PROD.OUTLOOK.COM> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 07bf366f-81c5-42e0-bc4e-08d80974d117 X-MS-Exchange-CrossTenant-originalarrivaltime: 05 Jun 2020 17:21:00.0665 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 6e725c29-763a-4f50-81f2-2e254f0133c8 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: /5PBFSacAcVAFblTtwb0moBIcuR8RYgc/9gT4EAM6QhlApe54vGNLCiRKVBRbocXQZlOp/4paJ9Tfu8x85ouUacvAsT2l6QrfK4eH07vx+M= X-MS-Exchange-Transport-CrossTenantHeadersStamped: LNXP265MB0505 X-OriginatorOrg: glasgow.ac.uk Sender: linux-man-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org Observed in CentOS 8's man-pages-4.15-6.el8.x86_64 and also on man-pages Gi= t master: Man-pages's rand.3 says rand() returns values in the range [0, RAND_MAX] an= d is very clear that this is inclusive. This is the same as the POSIX descr= iption of rand(3). Man-pages's random.3 says random() returns values "in the range from 0 to R= AND_MAX". However POSIX describes random() as returning values "in the rang= e from 0 to 2^31-1". In practice glibc and musl both fix RAND_MAX as a constant 2^31-1 so on the= se platforms it is the same thing. Similarly on macOS. It appears that Free= BSD used to have a slightly lower value of RAND_MAX but several months ago = raised it to 2^31-1 similarly. OTOH it appears that Windows, Cygwin, etc st= ill use a much smaller value for RAND_MAX (32767) but the full POSIX range = for random(3). So random.3 describing the range as 0..RAND_MAX is correct on Linux (unless= you're using a very unusual libc) but misleading when used as a reference = for writing code portable to other platforms. It would be good to change ra= ndom.3 to refer to the hardcoded constant (2^31-1) instead of RAND_MAX (and= perhaps add a note that on Linux this is the same as RAND_MAX), or at leas= t to add a note saying that RAND_MAX may be an unrelated value on other pla= tforms. Thanks, John=