From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 49523 invoked by alias); 12 Jun 2018 15:21:09 -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 49501 invoked by uid 89); 12 Jun 2018 15:21:08 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.4 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 spammy=discover, HContent-Transfer-Encoding:8bit X-HELO: smtp.polymtl.ca Received: from smtp.polymtl.ca (HELO smtp.polymtl.ca) (132.207.4.11) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 12 Jun 2018 15:21:07 +0000 Received: from simark.ca (simark.ca [158.69.221.121]) (authenticated bits=0) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id w5CFL1s2023008 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 12 Jun 2018 11:21:05 -0400 Received: by simark.ca (Postfix, from userid 112) id 30F871EF2A; Tue, 12 Jun 2018 11:21:01 -0400 (EDT) Received: from simark.ca (localhost [127.0.0.1]) by simark.ca (Postfix) with ESMTP id 3B0591E481; Tue, 12 Jun 2018 11:21:00 -0400 (EDT) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Tue, 12 Jun 2018 15:21:00 -0000 From: Simon Marchi To: Pedro Alves Cc: Alan Hayward , GDB Patches , Simon Marchi , nd Subject: Re: [PATCH v2 02/10] Add Aarch64 SVE Linux headers In-Reply-To: <0f4bd1b7-897f-b42a-3067-2397a1b4c58c@redhat.com> References: <20180606151629.36602-1-alan.hayward@arm.com> <20180606151629.36602-3-alan.hayward@arm.com> <9FBBFBF2-9363-49AA-8BC3-20E4E0AFBFED@arm.com> <5862fa9c22cc48d86256686e74d60f20@polymtl.ca> <82743c0795488492486076685b9f8828@polymtl.ca> <8f6d2b87-707a-3e34-325c-ed9338e9c1f6@redhat.com> <104a9ac067b435bd80a0b19fc638d0d0@polymtl.ca> <0f4bd1b7-897f-b42a-3067-2397a1b4c58c@redhat.com> Message-ID: X-Sender: simon.marchi@polymtl.ca User-Agent: Roundcube Webmail/1.3.6 X-Poly-FromMTA: (simark.ca [158.69.221.121]) at Tue, 12 Jun 2018 15:21:01 +0000 X-IsSubscribed: yes X-SW-Source: 2018-06/txt/msg00315.txt.bz2 On 2018-06-12 11:11, Pedro Alves wrote: > On 06/12/2018 04:06 PM, Simon Marchi wrote: >> I think that would be a good compromise.  By default, building on a >> machine with an older kernel would exclude SVE support.  But it would >> be possible to add it by pointing to the headers of a recent kernel.  >> So when building on a machine with an older kernel... >> >> - ... without any special flags, you don't get SVE support. >> - ... with just --enable-sve, you get a configure error. >> - ... with --enable-sve and CFLAGS/CXXFLAGS pointing to headers of a >> kernel w/ SVE macros, you get SVE support. >> >> Does that make sense? > Yes. Not sure an --enable-sve switch is necessary (compared to just > having > headers vs not having headers), but I'd be fine with having one. I think it is useful if you want to make sure your build will have the support: - auto/not specified: include the support if the prerequisites are available - enable: include the support, error at configure if prerequisites are missing - disable: don't include the support Otherwise, just a typo in your include path can result in a build without the feature you want, and you only discover it later, that's annoying. Simon