From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id E1A228032 for ; Wed, 3 Dec 2014 20:44:42 +0100 (CET) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP; 03 Dec 2014 08:45:54 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,508,1413270000"; d="scan'208";a="617953296" Received: from pgsmsx108.gar.corp.intel.com ([10.221.44.103]) by orsmga001.jf.intel.com with ESMTP; 03 Dec 2014 07:19:37 -0800 Received: from shsmsx104.ccr.corp.intel.com (10.239.4.70) by PGSMSX108.gar.corp.intel.com (10.221.44.103) with Microsoft SMTP Server (TLS) id 14.3.195.1; Wed, 3 Dec 2014 23:19:36 +0800 Received: from shsmsx101.ccr.corp.intel.com ([169.254.1.110]) by SHSMSX104.ccr.corp.intel.com ([169.254.5.182]) with mapi id 14.03.0195.001; Wed, 3 Dec 2014 23:19:35 +0800 From: "Qiu, Michael" To: "Richardson, Bruce" Thread-Topic: [PATCH] test-pmd: Fix pointer aliasing error Thread-Index: AQHQDuxQX/2B2GdrV0OV5lPAliaykw== Date: Wed, 3 Dec 2014 15:19:34 +0000 Message-ID: <533710CFB86FA344BFBF2D6802E60286C9C5BA@SHSMSX101.ccr.corp.intel.com> References: <1417606044-3432-1-git-send-email-michael.qiu@intel.com> <1417606099-3489-1-git-send-email-michael.qiu@intel.com> <20141203114258.GA2396@bricha3-MOBL3> <533710CFB86FA344BFBF2D6802E60286C9C531@SHSMSX101.ccr.corp.intel.com> <20141203145148.GB2396@bricha3-MOBL3> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" , Michael Qiu Subject: Re: [dpdk-dev] [PATCH] test-pmd: Fix pointer aliasing error X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Dec 2014 19:44:43 -0000 On 2014/12/3 22:51, Richardson, Bruce wrote:=0A= > On Wed, Dec 03, 2014 at 01:59:58PM +0000, Qiu, Michael wrote:=0A= >> On 2014/12/3 19:43, Richardson, Bruce wrote:=0A= >>> On Wed, Dec 03, 2014 at 07:28:19PM +0800, Michael Qiu wrote:=0A= >>>> app/test-pmd/csumonly.c: In function =91get_psd_sum=92:=0A= >>>> build/include/rte_ip.h:161: error: dereferencing pointer =91u16=92=0A= >>>> does break strict-aliasing rules=0A= >>>> build/include/rte_ip.h:157: note: initialized from here=0A= >>>> ...=0A= >>>>=0A= >>>> The root cause is that, compile enable strict aliasing by default,=0A= >>>> while in function rte_raw_cksum() try to convert 'const char *'=0A= >>>> to 'const uint16_t *'.=0A= >>>>=0A= >>> What compiler version is this with? Is there any other way to fix this= =0A= >>> other than disabling the compiler warnings. Turning off strict aliasing= may=0A= >>> affect performance as it reduces the number of optimizations that the c= ompiler=0A= >>> can perform.=0A= >> The compile version is:=0A= >>=0A= >> $ gcc -v=0A= >> Using built-in specs.=0A= >> Target: x86_64-redhat-linux=0A= >> ...=0A= >> gcc version 4.4.7 20120313 (Red Hat 4.4.7-4) (GCC)=0A= >>=0A= >>=0A= >> The OS is centos6.5 x86_64=0A= >>=0A= >>=0A= >> Actually, another possible solution is, as gcc manual shows, use union.= =0A= >> In function rte_raw_cksum() of lib/librte_net/rte_ip.h:=0A= >>=0A= >> static inline uint16_t=0A= >> rte_raw_cksum(const char *buf, size_t len){=0A= >> union {=0A= >> const char *ubuf;=0A= >> const uint16_t *uu16;=0A= >> } convert;=0A= >>=0A= >> convert.ubuf =3D buf;=0A= >> const uint16_t *u16 =3D convert.uu16;=0A= >> ...=0A= >> }=0A= >>=0A= >> This may be work, but not test yet.=0A= >>=0A= >> Any comments about this solution?=0A= > what happens if you make rte_raw_cksum take a void * (or const void *) pa= rameter=0A= > instead of "const char *"?=0A= =0A= "size_t len" is for type char, it is the the array size(for char array=0A= is byte numbers), if we use void *, the meaning maybe confuse I think.=0A= But it should work with other code change.=0A= =0A= Thanks,=0A= Michael=0A= >=0A= > /Bruce=0A= >=0A= =0A=