Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762206AbXF0SEU (ORCPT ); Wed, 27 Jun 2007 14:04:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757280AbXF0SEN (ORCPT ); Wed, 27 Jun 2007 14:04:13 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:56495 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756443AbXF0SEM (ORCPT ); Wed, 27 Jun 2007 14:04:12 -0400 Date: Wed, 27 Jun 2007 19:04:09 +0100 From: Al Viro To: Linus Torvalds Cc: Neil Booth , Josh Triplett , Segher Boessenkool , linux-kernel@vger.kernel.org, linux-sparse@vger.kernel.org Subject: Re: [PATCH 16/16] fix handling of integer constant expressions Message-ID: <20070627180408.GC21478@ftp.linux.org.uk> References: <1a25667a20e43a072f733a3ec2b8e79d@kernel.crashing.org> <20070624203837.GE21478@ftp.linux.org.uk> <467F531A.3030702@freedesktop.org> <20070626221040.GI21478@ftp.linux.org.uk> <20070626221134.GA21350@ftp.linux.org.uk> <20070627121021.GQ7590@daikokuya.co.uk> <20070627172903.GB21478@ftp.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1536 Lines: 35 On Wed, Jun 27, 2007 at 10:45:55AM -0700, Linus Torvalds wrote: > > > On Wed, 27 Jun 2007, Al Viro wrote: > > > > Eh... I'd say that my variant for offsetof() is simply better - it usually > > directly turns into EXPR_VALUE, right in place, without rather convoluted > > work. Aside of "should such cast be a constant integer expression"... > > Umm. But sparse is meant to parse C code. Which very much includes *other* > projects. > > The kernel, for example, has its own offsetof. And yes, these days we use > "__compiler_offsetof()", but we used to do > > #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) > > and I seriously doubt that the kernel is the only one doing things like > that. You can't have it both way, really. If we are talking about annotating a codebase we _can_ annotate, that one is not a problem at all. If we are talking about vanilla C project that never heard about sparse... We can define whatever extensions we like, but such project has to cope with whatever C compilers they had been using. So "sparse believes that this defintion of offsetof can be used as array size" will mean fsck-all outside of #ifdef __CHECKER__ and under such ifdef we can always define it to builtin; if anything, that will be faster and easier on sparse. - 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/