From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-x333.google.com (mail-ot1-x333.google.com [IPv6:2607:f8b0:4864:20::333]) by sourceware.org (Postfix) with ESMTPS id 05E3E38515F4 for ; Thu, 6 May 2021 12:09:28 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 05E3E38515F4 Received: by mail-ot1-x333.google.com with SMTP id f75-20020a9d03d10000b0290280def9ab76so4623983otf.12 for ; Thu, 06 May 2021 05:09:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=s908vXb7nga9ztJ+vP4PqF5FWaWYVZ+SWN16LVQaE3E=; b=ZrMWv3hRcFpNWVW/pMK7/ue4xLNaZAFj6++HaqG81ii5iiiUQoWKAxhOTL4RXllAdJ yP7kO7jjd3pRjbsB/ULU+E76yfQF9oIVmAOj9Zpv4oVJX/SPc4ghNXZXELvmJMVhV9i5 NIyPZkPoydlca5JFUK+Wf1r7ZohhaqSCKjzBCHeJoWa2blX2fgLiERPkrnc+J7sgu/p4 nv57EHD9tRDKkpxAllh+QPQ7PHNVUs4Tae1vNTi/7zwqM0zU/GljzUBrYVWw8Y0xLRj+ 5A1k4fFq7xANsYrp3L8wAbUcspwNXjB7lrWTae18aIxN9AWVagVj+wRWSevnS90gjho8 7MwA== X-Gm-Message-State: AOAM531UAbNM8q9mwoBHHEJkopoHMfVnn9Ni1kOJsl7611EnTzIbTDVu +5b36ti/i6oLUhzuOJNJR7gHH3rVDnHcxIF1MgBlp/BrnMM= X-Google-Smtp-Source: ABdhPJwGeBSzDIfYrWGFw9gmdNtEX5AwTJCp15v8w58amrQhQRzVIXd4cONRL4F9NZTfCpBy9w4NSkoFX/TDoV9mOng= X-Received: by 2002:a9d:67cf:: with SMTP id c15mr3236572otn.285.1620302967464; Thu, 06 May 2021 05:09:27 -0700 (PDT) MIME-Version: 1.0 References: <87eeelfg77.fsf@oldenburg.str.redhat.com> <87h7jhxasp.fsf@igel.home> <877dkdate3.fsf@oldenburg.str.redhat.com> <87zgx8i5l2.fsf@oldenburg.str.redhat.com> In-Reply-To: <87zgx8i5l2.fsf@oldenburg.str.redhat.com> From: "H.J. Lu" Date: Thu, 6 May 2021 05:08:51 -0700 Message-ID: Subject: Re: [PATCH v2] elf: Implement filtering of symbols historically defined in libpthread To: Florian Weimer Cc: Andreas Schwab , GNU C Library Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-3028.3 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, 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: Thu, 06 May 2021 12:09:29 -0000 On Thu, May 6, 2021 at 2:17 AM Florian Weimer wrote: > > * H. J. Lu: > > > On Wed, May 5, 2021 at 1:48 PM H.J. Lu wrote: > >> > >> On Wed, May 5, 2021 at 1:17 PM Florian Weimer via Libc-alpha > >> wrote: > >> > > >> > * Andreas Schwab: > >> > > >> > > When bison is rebuilt with a linker that contains binutils commit > >> > > b293661219c, it no longer crashes, and this patch isn't needed. > >> > > >> > Hmm. I worry we need to preserve compatibility with old binaries. = Not > >> > everyone can do distribution bootstrap or has the source code to car= ry > >> > it out. > >> > >> We never guarantee that applications linked against the old unversion > >> glibc work with the versioned glibc today. Otherwise, we don't need > >> glibc version at all. > > > > We can hide symbols for undefined, weak, unversioned references > > from the old versioned binaries. > > If it's okay to deliberately break backwards compatibility with some old > binaries, wouldn't we not use a patch at all? That's drop this patch > and just use what's currently in the tree? > > I'm not sure which group of old binaries is more important (deliberate > use of unversioned weak symbols in recent times vs binaries linked > against glibc 2.0 using the accidentally). If it's okay to break > things, I'm leaning towards =E2=80=9Cno patch=E2=80=9D (despite having sp= ent quite some > time on it). We should maintain backward compatibility with versioned binaries. For unversioned binaries, we can check DT_NEEDED with libpthread.so.6. > I may have to come back to this topic in a year or so, based on end user > feedback. Given that the symbol filter does not have ABI impact, it's a > backportable change, so I'm not too concerned to get this right > immediately. > > Thanks, > Florian > --=20 H.J.