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: AS17314 8.43.84.0/22 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, PDS_RDNS_DYNAMIC_FP,RCVD_IN_DNSWL_MED,RDNS_DYNAMIC,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 07E371F8C7 for ; Mon, 12 Jul 2021 15:07:52 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 013F6388A43E for ; Mon, 12 Jul 2021 15:07:51 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 013F6388A43E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1626102471; bh=g1UsB0yOlOFL2H73NcYL9bL1Y8OM0FiYTIfCVs+FQoE=; h=To:Subject:References:Date:In-Reply-To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=PK+r3WGLN2eVvP/KdQfUgWPnNNigceSb5uJGkaGLDfV6QBP7JPHs/urq+3I8e3Rgq caqiVyBznMbeXxixlnPjbE9UuB0/xYn6AD85hOVVnTDToqEWJBbcUZePzZUNgny+wN QEUyXCbx+Oft+YHPTM7KZvQOTj7i7S1dZHy55FNY= Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id 810A3388982A for ; Mon, 12 Jul 2021 15:03:47 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 810A3388982A 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-7-TPjKX6hjPpGQM-93MsHDVw-1; Mon, 12 Jul 2021 11:03:45 -0400 X-MC-Unique: TPjKX6hjPpGQM-93MsHDVw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 79C96EC1A0; Mon, 12 Jul 2021 15:03:44 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-103.rdu2.redhat.com [10.10.112.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0B5FC5D9DC; Mon, 12 Jul 2021 15:03:42 +0000 (UTC) To: Michael Hudson-Doyle Subject: Re: Undefined use of weak symbols in gnulib References: <87o8e0p92r.fsf@oldenburg.str.redhat.com> Date: Mon, 12 Jul 2021 17:03:40 +0200 In-Reply-To: (Michael Hudson-Doyle's message of "Mon, 12 Jul 2021 22:04:11 +1200") Message-ID: <87y2ab8tgz.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 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain 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: , From: Florian Weimer via Libc-alpha Reply-To: Florian Weimer Cc: bug-gnulib@gnu.org, libc-alpha@sourceware.org, binutils@sourceware.org Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" * Michael Hudson-Doyle: > Did this thread ever reach a conclusion? I'm testing a snapshot of > glibc 2.34 in ubuntu and running into this issue -- bison segfaults on > startup on ppc64el. For us it got resolved with a binutils fix: commit b293661219c36e72acb80502a86b51160bb88cfd Author: Alan Modra Date: Mon May 3 10:03:06 2021 +0930 PPC: ensure_undef_dynamic on weak undef only in plt It's slightly weird to have a call to a weak function not protected by a test of that function being non-NULL, but the non-NULL test might be covered by a test of another function. For example: if (func1) { func1 (); func2 (); } where func2 is known to exist if func1 exists. * elf32-ppc.c (allocate_dynrelocs): Call ensure_undef_dynamic for weak undefined symols that only appear on PLT relocs. * elf64-ppc.c (allocate_dynrelocs): Likewise. We rebuilt bison and a couple of other packages that looked like it would be affected by this before putting glibc 2.34 snapshots into the buildroot, and that worked quite well for us. (Thanks to Andreas Schwab for identifying the issue so early.) We don't know yet whether there are user binaries out there which will be incompatible with glibc 2.34. I have posted a glibc patch which alters symbol resolution to increase compatibility with old binaries (so it's technically feasible to get this working again), but in the review discussion, I was asked to break *more* older binaries, including every i386 binary from the late 1990s/early 2000s, so I dropped that patch and did not pursue this approach further. But I guess we can get back to it if feedback from end users indicates that the current approach doesn't work for them. Thanks, Florian