From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 21724D1D478 for ; Thu, 8 Jan 2026 15:27:57 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vdrvN-0007M7-2e; Thu, 08 Jan 2026 10:27:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vdrvL-0007Lr-01 for qemu-devel@nongnu.org; Thu, 08 Jan 2026 10:27:43 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vdrvJ-0006m0-C5 for qemu-devel@nongnu.org; Thu, 08 Jan 2026 10:27:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1767886060; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fZ136qR++A81Z/l2i0a5iNWWybBYz7B5WJ5N14ilHyI=; b=iiva22GEvYJewa67KBB/qZoAobogIrqv4BtnuqUsm0qmUxZKvtICSj5UUBhINW+qVi9iIc bQOWU5NjJyI8on/RakFDz6jmFiUFavcJBakiT2h/GI7W8fRZDxrNllkTml5ObAp34imiP/ 1/SJxIDf68jlDz3ahtzOE/l4wI0ujyM= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-422-b0hN_5KMNQO69LQ6kF-Urw-1; Thu, 08 Jan 2026 10:27:38 -0500 X-MC-Unique: b0hN_5KMNQO69LQ6kF-Urw-1 X-Mimecast-MFC-AGG-ID: b0hN_5KMNQO69LQ6kF-Urw_1767886057 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 515391955DC7; Thu, 8 Jan 2026 15:27:37 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.44]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5508C180066A; Thu, 8 Jan 2026 15:27:35 +0000 (UTC) Date: Thu, 8 Jan 2026 15:27:32 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Paolo Bonzini Cc: qemu-devel@nongnu.org, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Richard Henderson , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Subject: Re: [PATCH] meson: disable libatomic with GCC >= 16 Message-ID: References: <20260108141407.2151817-1-berrange@redhat.com> <56548949-8afd-4bcc-b539-bfb1a28c3987@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <56548949-8afd-4bcc-b539-bfb1a28c3987@redhat.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Jan 08, 2026 at 04:15:38PM +0100, Paolo Bonzini wrote: > On 1/8/26 15:14, Daniel P. Berrangé wrote: > > Historically it was required to ask for libatomic explicitly with > > -latomic, but with GCC >= 16 apps will get linked to libatomic > > whether they ask for it or not. > > > > This invalidates QEMU's check for atomic op support for int128 > > which explicitly does NOT want to use the libatomic impl. As a > > result with GCC >= 16, QEMU is now getting linked to libatomic > > and is activating CONFIG_ATOMIC128. This in turn exposes a bug > > in GCC's libatomic.a static buld which is incompatible with the > > use of -static-pie leading to build failures like: > > > > /usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/16/libatomic.a(cas_16_.o): relocation R_X86_64_32 against hidden symbol `libat_compare_exchange_16_i1' can not be used when making a PIE object > > /usr/bin/ld: failed to set dynamic section sizes: bad value > > collect2: error: ld returned 1 exit status > > > > The newly introduced -fno-link-libatomic flag can be used to > > disable the new automatic linking of libatomic. Setting this in > > qemu_isa_flags early on ensures that the check for CONFIG_ATOMIC128 > > still works correctly. > > > > Signed-off-by: Daniel P. Berrangé > > --- > > meson.build | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/meson.build b/meson.build > > index db87358d62..56df08c10e 100644 > > --- a/meson.build > > +++ b/meson.build > > @@ -445,6 +445,15 @@ if host_arch in ['i386', 'x86_64'] > > endif > > endif > > +# GCC >= 16 automatically tries to link libatomic for all programs. > > +# > > +# QEMU explicitly does NOT want to use libatomic for int128 types. > > +# > > +# Later checks assume we won't get atomic ops for int128 without > > +# explicitly asking for -latomic, so we must disable GCC's new > > +# automatic linking with the new -fno-link-libatomic flag > > +qemu_isa_flags += cc.get_supported_arguments('-fno-link-libatomic') > > + > > qemu_common_flags = qemu_isa_flags + qemu_common_flags > > if get_option('prefer_static') > > Great. :/ Is there a bug reported for the -static-pie issue? GCC maintainers tell me that -static-pie is unsupported for anything except libgcc.a / libstdc++.a: https://bugzilla.redhat.com/show_bug.cgi?id=2427891#c10 With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|