From owner-sc22wg14+sc22wg14-domo2=www.open-std.org@open-std.org Wed Sep 2 11:52:47 2026 Return-Path: X-Original-To: sc22wg14-domo2 Delivered-To: sc22wg14-domo2@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id D0127356E1E; Wed, 2 Sep 2026 11:52:47 +0200 (CEST) Delivered-To: sc22wg14@open-std.org Received: from mail3-relais-sop.national.inria.fr (mail3-relais-sop.national.inria.fr [192.134.164.104]) by www.open-std.org (Postfix) with ESMTP id 80287356CE7 for ; Wed, 2 Sep 2026 11:52:46 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=inria.fr; s=dc; h=date:from:to:cc:subject:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=I/QvUzdnF66/ceRrCwgy0g7egnAl8dL4KkiGfslO/Og=; b=C83T1wzYj3mt1qXuxD+4FhW3hK/zSH+x44fCTSFYf7VFSJb2jXXLF7te /6SjqYsUGfhEQQMZ9sjz0CLTnKsEKeYH/h6LOkoo8SAg/+O8EDjy6pJbH QMEck5Ff/eeeEgcdsJj+bGSSLPPwcUfG5qY6WM5ocI9eu9c1qGI64NonD Y=; X-CSE-ConnectionGUID: ov3Dr+yUQGCCUnd7pdO9BQ== X-CSE-MsgGUID: qizy0fpbRkaz49hafUMxZQ== Authentication-Results: mail3-relais-sop.national.inria.fr; dkim=none (message not signed) header.i=none; spf=SoftFail smtp.mailfrom=jens.gustedt@inria.fr; dmarc=fail (p=none dis=none) d=inria.fr X-IronPort-AV: E=Sophos;i="6.25,257,1779141600"; d="scan'208";a="155684072" Received: from lfbn-str-1-96-234.w92-140.abo.wanadoo.fr (HELO inria.fr) ([92.140.223.234]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2026 11:52:47 +0200 Date: Wed, 2 Sep 2026 11:52:45 +0200 From: =?UTF-8?B?SuKCkeKCmeKCmw==?= Gustedt To: Joseph Myers Cc: sc22wg14@open-std.org Subject: Re: [SC22WG14.37787] New issue #1103: Contradictory requirements of linkage Message-ID: <20260902115245.03e267fd@inria.fr> In-Reply-To: <20260901202541.12454356E47@www.open-std.org> References: <20260901202541.12454356E47@www.open-std.org> Organization: inria.fr X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) X-Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAAXNSR0IArs4c6QAAACRQTFRFERslNjAsLTE9Ok9wUk9TaUs8iWhSrYZkj42Rz6aD3sGZ MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-sc22wg14@open-std.org Precedence: bulk Hello, on Tue, 01 Sep 2026 20:25:35 +0000 you (Joseph Myers ) wrote: > The following new C standard issue has been submitted. >=20 > https://www.open-std.org/jtc1/sc22/wg14/issues/c23/issue1103.html >=20 > ## Issue 1103: Contradictory requirements of linkage >=20 > Authors: Jay Ghiron =20 > Date: 2026-09-01 =20 > Submitted against: C23 =20 > Status: Open >=20 > Consider the second declaration in the following: >=20 > ```c > static int x; > extern int x; > ``` >=20 > > For an identifier declared with the storage-class specifier `extern` > > in a scope in which a prior declaration of that identifier is > > visible, if the prior declaration specifies internal or external > > linkage, the linkage of the identifier at the later declaration is > > the same as the linkage specified at the prior declaration. If no > > prior declaration is visible, or if the prior declaration specifies > > no linkage, then the identifier has external linkage. =20 >=20 > (C23 6.2.2 "Linkages of identifiers" paragraph 4.) >=20 > There is a prior declaration visible with internal linkage, so > according to this paragraph the linkage should be internal. >=20 > > If the declaration of an identifier for a function has no > > storage-class specifier, its linkage is determined exactly as if it > > were declared with the storage-class specifier `extern`. If the > > declaration of an identifier for an object has file scope and does > > not contain the storage-class specifier `static` or `constexpr`, its > > linkage is external. =20 >=20 > (C23 6.2.2 "Linkages of identifiers" paragraph 5.) >=20 > The second declaration does have file scope and does not contain > either of the storage-class specifiers `static` or `constexpr`, so > according to this paragraph the linkage is external. >=20 > This wording was changed in C23 to work with type inference and > `thread_local` correctly, but it incorrectly also now covers the case > where `extern` is used. >=20 > ### Suggested correction >=20 > Modify C23 6.2.2 paragraph 5: >=20 > > If the declaration of an identifier for a function has no > > storage-class specifier, its linkage is determined exactly as if it > > were declared with the storage-class specifier `extern`. If the > > declaration of an identifier for an object has file scope and does > > not contain any of the storage-class specifiers > > `extern`, `static`, or `constexpr`, its linkage is > > external. =20 This would not solve the same problem that exists for function declarations. I'd rather suggest If an identifier for a function or object is declared with the storage class specifier `extern` where a prior declaration with linkage of that identifier is visible, the linkage of the identifier is the same as for the prior declaration. If the declaration of an identifier for a function has no storage-class specifier, its linkage is determined exactly as if it were declared with the storage-class specifier `extern`. If the declaration of an identifier for an object has file scope and does not contain the storage-class specifier `static` or `constexpr`, its linkage is external. Thanks J=E2=82=91=E2=82=99=E2=82=9B --=20 :: ICube :::::::::::::::::::::::::::::: deputy director :: :: Universit=C3=A9 de Strasbourg :::::::::::::::::::::: ICPS :: :: INRIA antenne de Strasbourg :::::::::::::::::: Camus :: :: INRIA PIQ program Strasbourg :::::::::: piq.inria.fr :: :: :::::::::::::::::::::::::::::::::::: =E2=98=8E +33 368854536 :: :: https://icube-icps.unistra.fr/index.php/Jens_Gustedt ::