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 5C6203858C83 for ; Wed, 22 Feb 2023 08:28:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 5C6203858C83 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677054493; 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=i7TCXf8o4mqxEYKKJkulYkeRoWe9kbMlcgnzkstMu7o=; b=btlbSuujxmjqopnzQsaG+43jxzVS8HScnroT0O9qJzROswwssYCRTtS5ZHSgNE5vLKUVWE dc5IbtQh+l7K8AqtHbJfVOSnCkNmgp+unxy07l7gBOESyTZrRd4CkFwRmvGm88e5jDhT9u QB/0259888INfMpeYu7Jne4FyPgvuC4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-654-OmQa5RMKMtmPlt0_Jsx5iA-1; Wed, 22 Feb 2023 03:28:09 -0500 X-MC-Unique: OmQa5RMKMtmPlt0_Jsx5iA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8197F85A588; Wed, 22 Feb 2023 08:28:09 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AA7302166B26; Wed, 22 Feb 2023 08:28:08 +0000 (UTC) From: Florian Weimer To: Richard Biener Cc: gcc@gcc.gnu.org Subject: Re: Using __gnu_lto_slim to detect -fno-fat-lto-objects References: <87a616un8q.fsf@oldenburg.str.redhat.com> Date: Wed, 22 Feb 2023 09:28:06 +0100 In-Reply-To: (Richard Biener's message of "Wed, 22 Feb 2023 09:23:45 +0100") Message-ID: <875ybuumsp.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-4.5 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_H2,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: * Richard Biener: > On Wed, Feb 22, 2023 at 9:19 AM Florian Weimer via Gcc wrote: >> >> Can we use the COMMON symbol __gnu_lto_slim to detect >> -fno-fat-lto-objects on contemporary GNU/Linux (with the LTO linker >> plugin)? > > Yes. Great, thanks. >> We currently build the distribution with -ffat-lto-objects, and I want >> to switch away from that. Packages will need to opt in to >> -ffat-lto-objects if static objects they build escape the buildroot. >> And to make sure that this opt-in happens, I want to fail the build if >> there would be any -fno-fat-lto-objects objects leaking. > > For SUSE we're checking that no LTO bytecode leaks instead, thus we check > for __gnu_lto_v? (I think). The reason is that even for static libraries > we do not want to ship LTO bytecode. We build with -ffat-lto-objects, and this means we can create perfectly fine object files by stripping the LTO data: This means that so far, we only had to fix LTO compilation problems in the packages, but not teach individual packages about LTO and non-LTO object files. Of course it's wasteful because few packages actually install the object files (without a final link into a program or shared object), and that's what I want to fix. Florian