From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by sourceware.org (Postfix) with ESMTPS id 1C8133858434 for ; Fri, 5 Nov 2021 13:35:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1C8133858434 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 5154F1FD37; Fri, 5 Nov 2021 13:35:21 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3146F13A2C; Fri, 5 Nov 2021 13:35:21 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id rO0WChkzhWHMagAAMHmgww (envelope-from ); Fri, 05 Nov 2021 13:35:21 +0000 Subject: Re: [PATCH] [gdb/testsuite] Fix gdb.arch/i386-avx.exp with clang To: Pedro Alves , Andrew Burgess Cc: gdb-patches@sourceware.org References: <20211104135559.5875-1-tdevries@suse.de> <20211105093300.GG918204@redhat.com> <20211105115404.GA1816063@redhat.com> <8074d4d8-fe21-bccf-3fb6-f4be2ea67f7b@palves.net> <1f6ed2db-5d31-9338-226e-3e1a5a7c225b@suse.de> From: Tom de Vries Message-ID: <4a98d0ce-b473-7a44-f399-3a604a5b2516@suse.de> Date: Fri, 5 Nov 2021 14:35:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-7.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Nov 2021 13:35:23 -0000 On 11/5/21 2:20 PM, Pedro Alves wrote: > On 2021-11-05 13:15, Tom de Vries wrote: >> On 11/5/21 1:55 PM, Pedro Alves wrote: >>> On 2021-11-05 12:23, Tom de Vries via Gdb-patches wrote: >>> >>>>> No, but in gdb/testsuite/lib/attribute.h we do setup a compatibility >>>>> macro for 'noclone', so there's definitely precedent for using >>>>> attributes that might not be supported everywhere. >>>>> >>>> >>>> Right, I'm aware of this, but that's a typical case where we have no >>>> portable alternative. >>> >>> We actually do -- _Alignas is standard C11. This fixes the test as well: >>> >>> _Alignas(32) v8sf_t data[] = >>> >> >> I was referring to the noclone, but ok, I was not aware of the _Alignas, >> good to know, thanks. >> >> Anyway, in the latest version this is not relevant anymore, since the >> precise alignment implementation has an extra benefit, as explained in >> the post. >> > > OOC, is that benefit important here? > So, this is the post I mentioned ( https://sourceware.org/pipermail/gdb-patches/2021-November/183183.html ). Well, the benefit is that it prevents accidental overalignment, which is the reason that this problem escaped detection and/or fixing for so long. Without that, I could do a thinko and specify too small an alignment and have the test passing accidentally, only to fail in a different setup. Thanks, - Tom