From owner-freebsd-hackers@freebsd.org Fri Apr 26 18:41:24 2019 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A65B2159B060 for ; Fri, 26 Apr 2019 18:41:24 +0000 (UTC) (envelope-from marklmi@yahoo.com) Received: from sonic316-20.consmr.mail.ne1.yahoo.com (sonic316-20.consmr.mail.ne1.yahoo.com [66.163.187.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1276380779 for ; Fri, 26 Apr 2019 18:41:22 +0000 (UTC) (envelope-from marklmi@yahoo.com) X-YMail-OSG: SF6bgPYVM1nhMKrYGanEkf9.42pcePyIudUezTwuz4SpcnaHvf8_JjZlU6ohyqO OVt7U8wC7ql3_lQ8VwoVFCcqItxp3LvuCxE44xJEGNAnhgPBizyPLfoYMuLvipwCW0Qnd2Ig38js aV6emwOLc.YrnClUkqov9wk08txxSUZfzuNR9Vhq09cU8Sh5Gf8zgp2gjwngj5JtVPuonP54k3rG M1ZTmojQQnYeyw3w0LSLSx9.zsZHOCBMiq_E4ipVfrKmrIxI2V3aBJijbQ96ZIz9eSzrxXqD06nz 5.H9RVi47PwSvx167J5vaJZeUi2E.qOsilbro.vPv8d9r76m3DHHPV66g2w8mb2jMxkpUw43Fm4. 4IDkM_Pq.I7LzdL3EgYup.eQRrmsomKQljAeAmX3F348VtETvQ.wT9mSVzAkxt10.Uk8LtxM_qAY khwm6T3.36df1s5eAeNeW_L7Hj9KZxhDGSVF3Im7M3Wyr3ZByPNeu7.0vxfPivBOZbwbBcbRpavb I0dcSe9FJeccohRCOD2fIy8oStPdHWQt6z5.0eXHryvGpPc_v5Go2bSRh6n4WNyodJTKvP4UUsZN HzQ3EPxXpHhu8EI8PoCnK_l9.IlX4furG.c5BYtZ5fJspo12y5r2VRLMhuzMKUbaii4i05.2CJok XReKnsZq8x2sxg4WBYMF6.w2fB6f92QmdtntMr096zqtrjGvB2iMCFYoX_zcjM3xed1Z7uSv_34e 8L5Q6OUkGcqDVOgvvLnvuAmGitUIEvisv7miIIzKcDpPewyCBmfr_dS5x7Y9KBI9Li8VJIXOIVIH EPaL7HoqkKtZ1RVVmhkhfFcu3xsSePVG2rL9zuynmoRp9A_mo_J.HHugTxxDGCQYZ4_O8XdZ5rt2 41LXhftHCk6guW7SOp2OsU2IAZk8cm2uSZ2lHO.MCZ1PtAmUzTVG6qB.VUOY2ux2St3IfXG5D3ev MPZ7LwDW9jLu7bCU4aRNgMGQsCn9GBK.UKELDAUPQvKWL22KUSerbX9KA4_6b9t27vbQJ26V4mbW .LYEQzDc7i8tZnZ.7H3mFcXel0v3Mee02jYI1vNVZpd.YyFW_6_MTVjuBTT3Cdq5DCYYh2vtzQjF sqKOVB3q47n8rR0VybULN.goixgA2W76QRtbVc9Bzdhb6KyjghDfFtUi58XfueAuyD3a7HFOpL8S nO1TfoS1wPDB. Received: from sonic.gate.mail.ne1.yahoo.com by sonic316.consmr.mail.ne1.yahoo.com with HTTP; Fri, 26 Apr 2019 18:41:21 +0000 Received: from c-76-115-7-162.hsd1.or.comcast.net (EHLO [192.168.1.103]) ([76.115.7.162]) by smtp403.mail.ne1.yahoo.com (Oath Hermes SMTP Server) with ESMTPA ID 5adbb87bd3271c1516d4bfb7215ac0fd; Fri, 26 Apr 2019 18:41:20 +0000 (UTC) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.8\)) Subject: Re: buf(9) woes: when does bcopy do nothing at all? From: Mark Millard In-Reply-To: <23438.1556267575@critter.freebsd.dk> Date: Fri, 26 Apr 2019 11:41:18 -0700 Cc: Alan Somers , FreeBSD Hackers Content-Transfer-Encoding: quoted-printable Message-Id: <6CF6472E-1100-475D-987C-071E916D64E8@yahoo.com> References: <23438.1556267575@critter.freebsd.dk> To: Poul-Henning Kamp X-Mailer: Apple Mail (2.3445.104.8) X-Rspamd-Queue-Id: 1276380779 X-Spamd-Bar: ++++ X-Spamd-Result: default: False [4.02 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_SPF_ALLOW(-0.20)[+ptr:yahoo.com]; MV_CASE(0.50)[]; FREEMAIL_FROM(0.00)[yahoo.com]; RCVD_COUNT_THREE(0.00)[3]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[yahoo.com:+]; MX_GOOD(-0.01)[cached: mta6.am0.yahoodns.net]; DMARC_POLICY_ALLOW(-0.50)[yahoo.com,reject]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_LAST(0.00)[]; FREEMAIL_ENVFROM(0.00)[yahoo.com]; SUBJECT_ENDS_QUESTION(1.00)[]; MID_RHS_MATCH_FROM(0.00)[]; ASN(0.00)[asn:36646, ipnet:66.163.184.0/21, country:US]; ARC_NA(0.00)[]; R_DKIM_ALLOW(-0.20)[yahoo.com:s=s2048]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; NEURAL_SPAM_SHORT(0.94)[0.939,0]; MIME_GOOD(-0.10)[text/plain]; DWL_DNSWL_NONE(0.00)[yahoo.com.dwl.dnswl.org : 127.0.5.0]; NEURAL_SPAM_MEDIUM(0.51)[0.513,0]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_SPAM_LONG(0.91)[0.905,0]; RCVD_IN_DNSWL_NONE(0.00)[146.187.163.66.list.dnswl.org : 127.0.5.0]; IP_SCORE(1.17)[ip: (3.40), ipnet: 66.163.184.0/21(1.41), asn: 36646(1.13), country: US(-0.06)]; RWL_MAILSPIKE_POSSIBLE(0.00)[146.187.163.66.rep.mailspike.net : 127.0.0.17] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 26 Apr 2019 18:41:24 -0000 On 2019-Apr-26, at 01:32, Poul-Henning Kamp wrote: > -------- > In message = , = Alan Somers writes: >=20 >> How is it possible that bcopy() doesn't affect its output array at = all? >=20 > That conclusion does not follow from your example: >=20 >> bcopy(cp, iov->iov_base, cnt); >> r =3D memcmp(cp, iov->iov_base, cnt); >> if (r) >> printf("uiomove: miscompare\n"); >=20 > If [cp:cp+cnt] and [iov_base:iov_base+cnt] overlap the bcopy result > is undefined. >=20 > Try memmove instead ? I only see a bcopy man page bcopy(3) but it says: DESCRIPTION The bcopy() function copies len bytes from string src to string = dst. The two strings may overlap. If len is zero, no bytes are copied. Is a kernel bcopy likely to be any different? =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)