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 3D6F332A5 for ; Mon, 8 Dec 2014 12:01:25 +0100 (CET) Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga102.fm.intel.com with ESMTP; 08 Dec 2014 03:01:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; d="scan'208";a="426429418" Received: from irsmsx110.ger.corp.intel.com ([163.33.3.25]) by FMSMGA003.fm.intel.com with ESMTP; 08 Dec 2014 02:50:41 -0800 Received: from irsmsx102.ger.corp.intel.com ([169.254.2.93]) by IRSMSX110.ger.corp.intel.com ([169.254.15.55]) with mapi id 14.03.0195.001; Mon, 8 Dec 2014 11:00:41 +0000 From: "Wodkowski, PawelX" To: "Qiu, Michael" , "dev@dpdk.org" Thread-Topic: error: value computed is not used Thread-Index: AdASxiisLi704rCnRgagZfyMuDIXlQADlEeA Date: Mon, 8 Dec 2014 11:00:41 +0000 Message-ID: References: <533710CFB86FA344BFBF2D6802E60286C9D989@SHSMSX101.ccr.corp.intel.com> In-Reply-To: <533710CFB86FA344BFBF2D6802E60286C9D989@SHSMSX101.ccr.corp.intel.com> Accept-Language: pl-PL, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.182] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] error: value computed is not used 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: Mon, 08 Dec 2014 11:01:25 -0000 > lib/librte_pmd_enic/enic_main.c: In function 'enic_set_rsskey': > lib/librte_pmd_enic/enic_main.c:862:2: error: value computed is not used >=20 > I dig out that, it was ome issue of the macros rte_memcpy() > #define rte_memcpy(dst, src, n) \ > ((__builtin_constant_p(n)) ? \ > memcpy((dst), (src), (n)) : \ > rte_memcpy_func((dst), (src), (n))) >=20 > When I use only (n) instead of (__builtin_constant_p(n), it will pass( I > know that it was incorrect, just a experiment). >=20 > But I try to use inline function instead of macros: > static inline void * rte_memcpy(void *dst, const void *src, size_t n) > { > return __builtin_constant_p(n) ? memcpy(dst, src, n) : > rte_memcpy_func(dst, src, n); > } >=20 > It will pass:), and works, this could be one potential workaround fix. >=20 > Who knows why? The root cause is what? >=20 > I've no idea about this. >=20 I got the same issue while ago. I don't remember exactly everything but my conclusion was that there was some bug in compiler. I think, when 'n' I constant and/or small compiler is inlining memcpy and throwing everything else (including returned value). In that case error is not produced (I think this is a bug in compiler). In other case it is computing some value calling memcpy or rte_ memcpy and you should at least explicitly throw it away by casting to void. I like solution with static inline but someone else should spoke about possible side effects. Pawel