From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16444 invoked by alias); 6 Oct 2014 08:41:37 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 16427 invoked by uid 89); 6 Oct 2014 08:41:36 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-Spam-User: qpsmtpd, 2 recipients X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Mon, 06 Oct 2014 08:41:35 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s968fUMH007063 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 6 Oct 2014 04:41:30 -0400 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s968fRPF027985; Mon, 6 Oct 2014 04:41:28 -0400 Message-ID: <543255B6.7060509@redhat.com> Date: Mon, 06 Oct 2014 08:41:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 MIME-Version: 1.0 To: Chen Gang , Joel Brobecker CC: Mark Kettenis , amodra@gmail.com, gbenson@redhat.com, michael.sturm@intel.com, walfred.tedeschi@intel.com, binutils@sourceware.org, gdb-patches@sourceware.org Subject: Re: [PATCH] gdb/i387-tdep.c: Avoid warning for "-Werror=strict-overflow" References: <542EC11C.3020406@gmail.com> <201410031546.s93FknOM002165@glazunov.sibelius.xs4all.nl> <542EC9FC.8050107@gmail.com> <20141003164420.GK6927@adacore.com> <542EE1BF.7060203@redhat.com> <542F831D.1000502@gmail.com> In-Reply-To: <542F831D.1000502@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2014-10/txt/msg00093.txt.bz2 On 10/04/2014 06:18 AM, Chen Gang wrote: > On 10/4/14 1:49, Pedro Alves wrote: >> On 10/03/2014 05:44 PM, Joel Brobecker wrote: >>>>> Sorry, but obfuscating code to make compilers happy is *not* the way to go. >>>>> >>>> >>>> OK, I can understand, but for me, these is no other better ways for it, >>>> except let gdb give up "-Werror" (if always need "--disable-werror" >>>> during "configure"). >>> >>> I have to agree with Mark on this one, the proposed solution looks >>> awful. There has to be another way. Maybe declaring a local constant >>> whose value is I387_XMM0_REGNUM (tdep)? >> >> Likely, after transformations and intra-procedural analyses, gcc would >> end up with the same. >> >> This: >> >> for (i = I387_ST0_REGNUM (tdep); i < I387_XMM0_REGNUM (tdep); i++) >> >> always iterates exactly 16 times, because I387_XMM0_REGNUM >> is defined like: >> >> #define I387_XMM0_REGNUM(tdep) (I387_ST0_REGNUM (tdep) + 16) >> >> An alternative I think might work would be to give that magic >> 16 constant a name, say: >> >> #define I387_NUM_ST_REGS 16 >> >> and then do: >> >> for (i = 0; i < i < I387_NUM_ST_REGS; i++) >> { >> int r = I387_ST0_REGNUM (tdep) + i; >> >> ... use 'r' instead of 'i' ... >> } >> > > OK, thanks. It is really one way, it is a little better than my original > way. But for me, it is still not a good idea: it introduces a new macro > and a new variable for each area (originally, it is only one statement). I see no problem with adding the new macro. We already have a ton of similar macros, see i386-tdep.h and i387-tdep.h. Looks like the existing I387_NUM_REGS is what we'd need here? BTC, OOC, did you try Joel's idea with the local variable? In case Mark prefers that, it'd be good to know whether it works. I can't seem to get my gcc to emit that warning. Combining both ideas, for clarity, we end up with something like: int end; end = I387_ST0_REGNUM (tdep) + I387_NUM_REGS; for (i = I387_ST0_REGNUM (tdep); i < end; i++) ... end = I387_XMM0_REGNUM (tdep) + I387_NUM_XMM_REGS (tdep); for (i = I387_XMM0_REGNUM (tdep); i < end; i++) That's way clearer to me than the existing: for (i = I387_ST0_REGNUM (tdep); i < I387_XMM0_REGNUM (tdep); i++) ... for (i = I387_XMM0_REGNUM (tdep); i < I387_MXCSR_REGNUM (tdep); i++) anyway, which assumes the reader knows register numbers are ordered like st -> xmm -> mxcrsr. If this works, I think it's my preference. > For me, "-Werror" need always be optional, but not mandatory. It's mandatory only on development builds. -Werror is not on by default on released GDBs. Thanks, Pedro Alves