From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757453AbYDTXA3 (ORCPT ); Sun, 20 Apr 2008 19:00:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753151AbYDTXAT (ORCPT ); Sun, 20 Apr 2008 19:00:19 -0400 Received: from ozlabs.org ([203.10.76.45]:56536 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753144AbYDTXAR (ORCPT ); Sun, 20 Apr 2008 19:00:17 -0400 From: Rusty Russell To: linux-kernel@vger.kernel.org Subject: [PATCH 1/6] cast_if_type: allow macros functions which take more than one type. Date: Mon, 21 Apr 2008 09:00:16 +1000 User-Agent: KMail/1.9.9 Cc: Andrew Morton , Al Viro , Linus Torvalds References: <200804210859.00080.rusty@rustcorp.com.au> In-Reply-To: <200804210859.00080.rusty@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200804210900.16242.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To create functions which can take two types, but still warn on any other types, we need a way of casting one type and no others. To make things more complex, it should correctly handle function args, NULL, and be usable in initializers. __builtin_choose_expr was introduced in gcc 3.1 (kernel needs >= 3.2 anyway). Signed-off-by: Rusty Russell --- include/linux/compiler-gcc.h | 19 +++++++++++++++++++ include/linux/compiler-intel.h | 2 ++ 2 files changed, 21 insertions(+) diff -r bde8a949d956 include/linux/compiler-gcc.h --- a/include/linux/compiler-gcc.h Mon Apr 07 15:27:30 2008 +1000 +++ b/include/linux/compiler-gcc.h Mon Apr 07 16:19:49 2008 +1000 @@ -53,3 +53,22 @@ #define noinline __attribute__((noinline)) #define __attribute_const__ __attribute__((__const__)) #define __maybe_unused __attribute__((unused)) + +/** + * cast_if_type - allow an alternate type + * @expr: the expression to optionally cast + * @oktype: the type to allow. + * @desttype: the type to cast to. + * + * This is used to accept a particular alternate type for an expression: + * because any other types will not be cast, they will cause a warning as + * normal. + * + * Note that the unnecessary trinary forces functions to devolve into + * function pointers as users expect, but means @expr must be a pointer or + * integer. + */ +#define cast_if_type(expr, oktype, desttype) \ + __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0),\ + oktype), \ + (desttype)(expr), (expr)) diff -r bde8a949d956 include/linux/compiler-intel.h --- a/include/linux/compiler-intel.h Mon Apr 07 15:27:30 2008 +1000 +++ b/include/linux/compiler-intel.h Mon Apr 07 16:19:49 2008 +1000 @@ -29,3 +29,5 @@ #endif #define uninitialized_var(x) x + +#define cast_if_type(expr, oktype, desttype) ((desttype)(expr))