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 593F08040 for ; Mon, 8 Dec 2014 16:24:53 +0100 (CET) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP; 08 Dec 2014 07:23:42 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,539,1413270000"; d="scan'208";a="634468756" Received: from pgsmsx104.gar.corp.intel.com ([10.221.44.91]) by fmsmga001.fm.intel.com with ESMTP; 08 Dec 2014 07:23:39 -0800 Received: from shsmsx103.ccr.corp.intel.com (10.239.4.69) by PGSMSX104.gar.corp.intel.com (10.221.44.91) with Microsoft SMTP Server (TLS) id 14.3.195.1; Mon, 8 Dec 2014 23:23:36 +0800 Received: from shsmsx101.ccr.corp.intel.com ([169.254.1.110]) by SHSMSX103.ccr.corp.intel.com ([169.254.4.240]) with mapi id 14.03.0195.001; Mon, 8 Dec 2014 23:23:35 +0800 From: "Qiu, Michael" To: "Wodkowski, PawelX" , "dev@dpdk.org" Thread-Topic: error: value computed is not used Thread-Index: AdASxiisLi704rCnRgagZfyMuDIXlQ== Date: Mon, 8 Dec 2014 15:23:34 +0000 Message-ID: <533710CFB86FA344BFBF2D6802E60286C9DB8B@SHSMSX101.ccr.corp.intel.com> References: <533710CFB86FA344BFBF2D6802E60286C9D989@SHSMSX101.ccr.corp.intel.com> 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 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 15:24:54 -0000 On 2014/12/8 19:00, Wodkowski, PawelX wrote:=0A= >> lib/librte_pmd_enic/enic_main.c: In function =91enic_set_rsskey=92:=0A= >> lib/librte_pmd_enic/enic_main.c:862:2: error: value computed is not used= =0A= >>=0A= >> I dig out that, it was ome issue of the macros rte_memcpy()=0A= >> #define rte_memcpy(dst, src, n) \=0A= >> ((__builtin_constant_p(n)) ? \=0A= >> memcpy((dst), (src), (n)) : \=0A= >> rte_memcpy_func((dst), (src), (n)))=0A= >>=0A= >> When I use only (n) instead of (__builtin_constant_p(n), it will pass( I= =0A= >> know that it was incorrect, just a experiment).=0A= >>=0A= >> But I try to use inline function instead of macros:=0A= >> static inline void * rte_memcpy(void *dst, const void *src, size_t n)=0A= >> {=0A= >> return __builtin_constant_p(n) ? memcpy(dst, src, n) :=0A= >> rte_memcpy_func(dst, src, n);= =0A= >> }=0A= >>=0A= >> It will pass:), and works, this could be one potential workaround fix.= =0A= >>=0A= >> Who knows why? The root cause is what?=0A= >>=0A= >> I've no idea about this.=0A= >>=0A= > I got the same issue while ago. I don't remember exactly everything=0A= > but my conclusion was that there was some bug in compiler. I think,=0A= > when 'n' I constant and/or small compiler is inlining memcpy and throwing= =0A= > everything else (including returned value). In that case error is not=0A= > produced (I think this is a bug in compiler). In other case it is computi= ng=0A= > some value calling memcpy or rte_ memcpy and you should at least=0A= > explicitly throw it away by casting to void. I like solution with static= =0A= =0A= Actually, I try to pass "n" as a Int value like 4, it still report this=0A= error :)=0A= =0A= > inline but someone else should spoke about possible side effects.=0A= =0A= Yes, but as I know inline is better than macros.=0A= =0A= Thanks,=0A= Michael=0A= >=0A= > Pawel=0A= >=0A= >=0A= =0A=