From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 0397C3858C36 for ; Tue, 2 Apr 2024 12:38:47 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 0397C3858C36 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 0397C3858C36 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1712061529; cv=none; b=fNiYSDGn4615SNA4ObOUVUIEOTUp6n8lP9eTEugbZnDoP1JtFCut6ShlDTi42FeSJKoWSfA0LSDOH3fGhV4cHq50SFpisRklY1A/dlCLFaLTduU7KXwWbZWmwJwrlyPH1UTyh4WW5L/TdI0SO2jpYBQhgkoYcW5yp0Fk/RmoRSc= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1712061529; c=relaxed/simple; bh=tKOccYCFI3hJYHplwX7lDL7YZk5DMCj9IzBGXoD0L3Q=; h=DKIM-Signature:From:To:Subject:Date:Message-ID:MIME-Version; b=q5x8Y06x8J2taeWD3bTyOQCVgujiTEX63dfXuPBDOdnjqCeOJayGhyXTv7sWTPTJb8fvNrIn74mscD3Doar8WGA2k03Ut7BGnQQspvbpl8rs/4QhsQYZ5yKNVQbz1kBvUS+Wr13cXwZR0ePXYFUgdwV145jLXISspW+M4EYMXj8= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712061527; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=u2vcS9XfXu8t1tNAzFGoFZTQdzygEC9lvpoQ3stZfMM=; b=Ny8NQLvaHTETWkSKg+5SpNWLKVOyszngRJ87cDz04zIVN5f6DLZcWvpzKaODkmiqKmNz6s LJQW3W+efqLNbsIAu4W2ZSLjiFEZrgmuHH7MUewxjvbx3GZ6nFu6B1PXxmLKnUy/lCi/No bOmSoXKNQG5//7lDULx1+r2XzTTHKbQ= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-18-PBi-dCp4OfiRC3OTDLOSog-1; Tue, 02 Apr 2024 08:38:45 -0400 X-MC-Unique: PBi-dCp4OfiRC3OTDLOSog-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8710F383CD72; Tue, 2 Apr 2024 12:38:44 +0000 (UTC) Received: from oldenburg3.str.redhat.com (unknown [10.39.192.250]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D813D1C060CE; Tue, 2 Apr 2024 12:38:43 +0000 (UTC) From: Florian Weimer To: Simon Chopin Cc: gcc-patches@gcc.gnu.org Subject: Re: [PATCH] libquadmath: printf: fix misaligned access on args References: <20240312190352.3455451-1-simon.chopin@canonical.com> Date: Tue, 02 Apr 2024 14:38:38 +0200 In-Reply-To: <20240312190352.3455451-1-simon.chopin@canonical.com> (Simon Chopin's message of "Tue, 12 Mar 2024 20:03:52 +0100") Message-ID: <87a5mcx7ld.fsf@oldenburg3.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-4.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: * Simon Chopin: > On x86, this compiles into movdqa which segfaults on unaligned access. > > This kind of failure has been seen when running against glibc 2.39, > which incidentally changed the printf implementation to move away from > alloca() for this data to instead append it at the end of an existing > "scratch buffer", with arbitrary alignement, whereas alloca() was > probably more likely to be naturally aligned. This glibc change appears to be incorrect. I think we need to preserve ABI alignment for types than can be passed through the vararg interface. I'm not sure if this easily possible, though. Certainly needs a discussion on libc-alpha. Thanks, Florian