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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A174C43387 for ; Fri, 18 Jan 2019 16:00:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4D5DA208E4 for ; Fri, 18 Jan 2019 16:00:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727850AbfARQAo (ORCPT ); Fri, 18 Jan 2019 11:00:44 -0500 Received: from foss.arm.com ([217.140.101.70]:60308 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727467AbfARQAm (ORCPT ); Fri, 18 Jan 2019 11:00:42 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1E4F41596; Fri, 18 Jan 2019 08:00:42 -0800 (PST) Received: from e119886-lin.cambridge.arm.com (unknown [10.37.6.11]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AACE33F557; Fri, 18 Jan 2019 08:00:39 -0800 (PST) From: Andrew Murray To: Masahiro Yamada , Arnd Bergmann , Kees Cook , Andrew Morton Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, Grant Likely , Steven Price , Dave P Martin Subject: [PATCH 1/3] kconfig.h: abstract empty functions with STUB_UNLESS macro Date: Fri, 18 Jan 2019 16:00:28 +0000 Message-Id: <1547827230-55132-2-git-send-email-andrew.murray@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1547827230-55132-1-git-send-email-andrew.murray@arm.com> References: <1547827230-55132-1-git-send-email-andrew.murray@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A common pattern found in header files is a function declaration dependent on a CONFIG_ option being enabled, followed by an empty function for when that option isn't enabled. This can often take up a lot of space and impact code readability. Let's introduce the following STUB_UNLESS macro: STUB_UNLESS(CONFIG_FOO, [body], prototype) This evaluates to 'prototype' prepended with 'extern' if CONFIG_FOO is set to 'y'. Otherwise it will evaluate to 'prototype' prepended with 'static inline' followed by an empty function body. Where optional argument 'body' then 'body' will be used as the function body, intended to allow for simple return statements. Signed-off-by: Andrew Murray --- include/linux/kconfig.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h index cc8fa10..216a27f 100644 --- a/include/linux/kconfig.h +++ b/include/linux/kconfig.h @@ -12,6 +12,7 @@ #define __ARG_PLACEHOLDER_1 0, #define __take_second_arg(__ignored, val, ...) val +#define __take_fourth_arg(__ignored, __ignored2, __ignored3, val, ...) val /* * The use of "&&" / "||" is limited in certain expressions. @@ -70,4 +71,34 @@ */ #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option)) + + +/* + * Allow for __stub to be overloaded by making the second argument optional + */ +#define __stub_overload(...) __take_fourth_arg(__VA_ARGS__, \ + __stub_body, __stub_void)(__VA_ARGS__) +#define __stub_body(option, body, ptype) __stub(option, body, ptype) +#define __stub_void(option, ptype) __stub(option, , ptype) + +/* + * Using the same trick as __defined we use the config option to conditionally + * expand to an extern function declaration or a static stub function. + */ +#define __stub(option, body, ptype) ___stub( \ + __ARG_PLACEHOLDER_##option, body, ptype) +#define ___stub(arg1_or_junk, body, ptype) __take_second_arg( \ + arg1_or_junk __extern_ptype(ptype), __static_ptype(body, ptype)) +#define __static_ptype(body, ptype) static inline ptype { body; } +#define __extern_ptype(ptype) extern ptype + +/* + * STUB_UNLESS(CONFIG_FOO, [body], prototype) evaluates to 'prototype' prepended + * with 'extern' if CONFIG_FOO is set to 'y'. Otherwise it will evaluate to + * 'prototype' prepended with 'static inline' followed by an empty function + * body. Where optional argument 'body' is present then 'body' will be used + * as the function body, intended to allow for simple return statements. + */ +#define STUB_UNLESS(...) __stub_overload(__VA_ARGS__) + #endif /* __LINUX_KCONFIG_H */ -- 2.7.4