From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS22989 209.51.188.0/24 X-Spam-Status: No, score=-3.8 required=3.0 tests=AWL,BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=unavailable autolearn_force=no version=3.4.2 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id E71251F5AE for ; Wed, 28 Apr 2021 08:35:21 +0000 (UTC) Received: from localhost ([::1]:43982 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lbffE-00017y-MO for normalperson@yhbt.net; Wed, 28 Apr 2021 04:35:20 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57926) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lbff4-00017q-Qj for bug-gnulib@gnu.org; Wed, 28 Apr 2021 04:35:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:50636) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lbfex-0002vv-Uo for bug-gnulib@gnu.org; Wed, 28 Apr 2021 04:35:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619598900; 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=Z9/hZ6krZKYTXq6vXFYjr/hwj0qEF73f7m0JHhtli7Y=; b=EVE3N3UYhawcaD9DJiZSurj0U/48F8YCfP0pwtFDuRYzwOmAb3cp/A5sI+Dpf5ThdDVL5S YVF6DZjLbimcbekq1Ar/IrsAPK/XJypjemxa0mpzUvOPILlYn87tzTwWdTVr1qq+Ns+I7F UgOGstWHrNgpWO4+OHNtdWpNgIti1aM= 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-110-Ldv4WOp7Ng-NKlqJSJrhQg-1; Wed, 28 Apr 2021 04:34:58 -0400 X-MC-Unique: Ldv4WOp7Ng-NKlqJSJrhQg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EB36F10054F6; Wed, 28 Apr 2021 08:34:56 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-113-20.ams2.redhat.com [10.36.113.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0104F70580; Wed, 28 Apr 2021 08:34:54 +0000 (UTC) From: Florian Weimer To: "H.J. Lu via Libc-alpha" Subject: Re: Undefined use of weak symbols in gnulib References: <87o8e0p92r.fsf@oldenburg.str.redhat.com> <87fszc8a1z.fsf@igel.home> <87eeewnfzw.fsf@oldenburg.str.redhat.com> <1680226.UWtE2gOZdF@omega> Date: Wed, 28 Apr 2021 10:35:24 +0200 In-Reply-To: (H. J. Lu via Libc-alpha's message of "Tue, 27 Apr 2021 19:10:56 -0700") Message-ID: <87h7jqkdrn.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=fweimer@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=170.10.133.124; envelope-from=fweimer@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.218, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: bug-gnulib@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Gnulib discussion list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "H.J. Lu" , Andreas Schwab , bug-gnulib@gnu.org, Bruno Haible , Binutils Errors-To: bug-gnulib-bounces+normalperson=yhbt.net@gnu.org Sender: "bug-gnulib" * H. J. Lu via Libc-alpha: > Alan extended the fix to PPC: > > commit 954b63d4c8645f86e40c7ef6c6d60acd2bf019de > Author: Alan Modra > Date: Wed Apr 19 01:26:57 2017 +0930 > > Implement -z dynamic-undefined-weak > > -z nodynamic-undefined-weak is only implemented for x86. (The sparc > backend has some support code but doesn't enable the option by > including ld/emulparams/dynamic_undefined_weak.sh, and since the > support looks like it may be broken I haven't enabled it.) This patch > adds the complementary -z dynamic-undefined-weak, extends both options > to affect building of shared libraries as well as executables, and > adds support for the option on powerpc. I'm not sure if this option is compatible with all compilers on POWER. The old binutils behavior allowed the compiler to optimize this common pattern void f1 (void) __attribute__ ((weak)); void f2 (void) { if (f1 != 0) f1 (); } into an unconditional call to f1 because the linker would replace the call with a NOP if the symbol is undefined, reproducing the effect of the if condition. However, GCC 10 does not appear to perform this optimization on powerpc64le. Thanks, Florian