Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755204AbXAAOU0 (ORCPT ); Mon, 1 Jan 2007 09:20:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755203AbXAAOU0 (ORCPT ); Mon, 1 Jan 2007 09:20:26 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:57764 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755204AbXAAOUZ (ORCPT ); Mon, 1 Jan 2007 09:20:25 -0500 Date: Mon, 1 Jan 2007 14:20:20 +0000 From: Christoph Hellwig To: "Robert P. J. Day" Cc: Linux kernel mailing list , Randy Dunlap , trivial@kernel.org Subject: Re: [PATCH] Documentation: Explain a second alternative for multi-line macros. Message-ID: <20070101142020.GA16425@infradead.org> Mail-Followup-To: Christoph Hellwig , "Robert P. J. Day" , Linux kernel mailing list , Randy Dunlap , trivial@kernel.org References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1070 Lines: 37 On Sun, Dec 31, 2006 at 02:32:25PM -0500, Robert P. J. Day wrote: > + (a) Enclose those statements in a do - while block: > + > + #define macrofun(a, b, c) \ > + do { \ > + if (a == 5) \ > + do_this(b, c); \ > + } while (0) nitpick, please don't add an indentaion level for the do {. Do this should look like: #define macrofun(a, b, c) \ do { \ if (a == 5) \ do_this(b, c); \ } while (0) > + (b) Use the gcc extension that a compound statement enclosed in > + parentheses represents an expression: > + > + #define macrofun(a, b, c) ({ \ > if (a == 5) \ > do_this(b, c); \ > - } while (0) > + }) I'd rather document to not use this - it makes the code far less redable. And it's a non-standard extension, something we only use if it provides us a benefit which it doesn't here. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/