Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753074AbZI3GfT (ORCPT ); Wed, 30 Sep 2009 02:35:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752905AbZI3GfR (ORCPT ); Wed, 30 Sep 2009 02:35:17 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:50975 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257AbZI3GfQ convert rfc822-to-8bit (ORCPT ); Wed, 30 Sep 2009 02:35:16 -0400 Message-Id: <4AC318450200007800017355@vpn.id2.novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.1 Date: Wed, 30 Sep 2009 07:35:17 +0100 From: "Jan Beulich" To: "Hollis Blanchard" Cc: , , , , , Subject: Re: linux-next: tree build failure References: <4AC1E15502000078000516B5@vpn.id2.novell.com> <1254267572.15622.1621.camel@slab.beaverton.ibm.com> In-Reply-To: <1254267572.15622.1621.camel@slab.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1554 Lines: 34 >>> Hollis Blanchard 30.09.09 01:39 >>> >On Tue, 2009-09-29 at 10:28 +0100, Jan Beulich wrote: >> >>> Hollis Blanchard 09/29/09 2:00 AM >>> >> >First, I think there is a real bug here, and the code should read like >> >this (to match the comment): >> > /* type has to be known at build time for optimization */ >> >- BUILD_BUG_ON(__builtin_constant_p(type)); >> >+ BUILD_BUG_ON(!__builtin_constant_p(type)); >> > >> >However, I get the same build error *both* ways, i.e. >> >__builtin_constant_p(type) evaluates to both 0 and 1? Either that, or >> >the new BUILD_BUG_ON() macro isn't working... >> >> No, at this point of the compilation process it's neither zero nor one, >> it's simply considered non-constant by the compiler at that stage >> (this builtin is used for optimization, not during parsing, and the >> error gets generated when the body of the function gets parsed, >> not when code gets generated from it). > >I think I see what you're saying. Do you have a fix to suggest? The one Rusty suggested the other day may help here. I don't like it as a drop-in replacement for BUILD_BUG_ON() though (due to it deferring the error generated to the linking stage), I'd rather view this as an improvement to MAYBE_BUILD_BUG_ON() (which should then be used here). Jan -- 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/