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 [63.128.21.124]) by sourceware.org (Postfix) with ESMTP id 0F7293861847 for ; Mon, 21 Dec 2020 09:33:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 0F7293861847 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-38-BSTb14uQOeStWUOQbSoZ3A-1; Mon, 21 Dec 2020 04:33:15 -0500 X-MC-Unique: BSTb14uQOeStWUOQbSoZ3A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B611259; Mon, 21 Dec 2020 09:33:14 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-120.ams2.redhat.com [10.36.112.120]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BC93310023BD; Mon, 21 Dec 2020 09:33:10 +0000 (UTC) From: Florian Weimer To: Paul Eggert Cc: Carlos O'Donell , libc-alpha@sourceware.org Subject: Re: [PATCH] free: preserve errno [BZ#17924] References: <20201220202556.3714-1-eggert@cs.ucla.edu> Date: Mon, 21 Dec 2020 10:33:09 +0100 In-Reply-To: (Paul Eggert's message of "Sun, 20 Dec 2020 23:20:33 -0800") Message-ID: <871rfjzep6.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.0 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_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Dec 2020 09:33:19 -0000 * Paul Eggert: > +/* The indirection through a volatile function pointer is necessary to prevent > + a GCC optimization. Without it, when optimizing, GCC would "know" that errno > + is unchanged by calling free(ptr), when ptr was the result of a malloc(...) > + call in the same function. */ > +static int > +get_errno (void) Long line (80 characters). I think you need to use this: int __attribute__ ((weak)) get_errno (void) { return errno; } With that volatile construct, the read of errno is not actually behind a compiler barrier. Thanks, Florian -- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill