From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751822Ab2JFElK (ORCPT ); Sat, 6 Oct 2012 00:41:10 -0400 Received: from nm1-vm0.bullet.mail.sp2.yahoo.com ([98.139.91.202]:45798 "HELO nm1-vm0.bullet.mail.sp2.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750846Ab2JFElG (ORCPT ); Sat, 6 Oct 2012 00:41:06 -0400 X-Yahoo-Newman-Id: 792531.38749.bm@omp1017.access.mail.sp2.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: opxT9xgVM1mqIpGRBGIQeJRpteSxF1riym6JO8A5_poyJ7F P7S0DqwgWXCp_CDGSpifc6w5WPmvBwVzJ718dfU.5_Xgj4cGD.UWrY57xzjk xjcdcB4YDgc7AFknU9mEFeb8T_tzHB4HcMB25W8xPNB1ht4opO8HOV7ly.5M ghvU0EDuJUDXfb4ReO4Imxg4BhgHwodTJiX_vX2DYOiRjSN.WiT0GMAwGH2v Tzw.O.PCn.ea_DjzKH5qM0LMDi82_ecemU7etLKdbr2dbTRykq07xIEEDx_H NQuyv6jVT__oqOFoVJv5sblabk6RNS7318GE7GkqbYd0CThcQdd3jJCoRyvG wKvuOjW8iPYXwR.SBKfHnVMovepbM3TkpfzjE8pzozkzb78cgHlbPIdSCplG Ow5ebgXc2jZpACXf7YWXLeGVlvwBVKKyP2aQbWS7tipH1BdhaRA-- X-Yahoo-SMTP: xXkkXk6swBBAi.5wfkIWFW3ugxbrqyhyk_b4Z25Sfu.XGQ-- Message-ID: <506FB65D.70109@att.net> Date: Fri, 05 Oct 2012 23:41:01 -0500 From: Daniel Santos Reply-To: Daniel Santos User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.4) Gecko/20120502 Thunderbird/10.0.4 MIME-Version: 1.0 To: Josh Triplett CC: Borislav Petkov , LKML , Andi Kleen , Andrea Arcangeli , Andrew Morton , Christopher Li , David Daney , David Howells , David Rientjes , Joe Perches , Konstantin Khlebnikov , linux-sparse@vger.kernel.org, Michel Lespinasse , Paul Gortmaker , Pavel Pisa , Peter Zijlstra , Steven Rostedt , Daniel Santos Subject: Re: [PATCH v2 09/10] bug.h: Add BUILD_BUG_ON_MSG & BUILD_BUG_INTERNAL{,2} References: <1349465759-20524-1-git-send-email-daniel.santos@pobox.com> <1349466169-20637-9-git-send-email-daniel.santos@pobox.com> <20121005205858.GB28452@liondog.tnic> <20121005210258.GB7362@jtriplet-mobl1> In-Reply-To: <20121005210258.GB7362@jtriplet-mobl1> X-Enigmail-Version: 1.3.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/05/2012 04:02 PM, Josh Triplett wrote: > On Fri, Oct 05, 2012 at 10:58:58PM +0200, Borislav Petkov wrote: >> On Fri, Oct 05, 2012 at 02:42:48PM -0500, danielfsantos@att.net wrote: >>> Add BUILD_BUG_ON_MSG which behaves like BUILD_BUG_ON (with optimizations >>> turned enabled), except that it allows you to specify the error message >>> you want emitted as the third parameter. Under the hood, this relies on >>> BUILD_BUG_INTERNAL{,2}, which does the actual work and is pretty-much >>> identical to BUILD_BUG_ON. >>> >>> Signed-off-by: Daniel Santos >>> --- >>> include/linux/bug.h | 26 ++++++++++++++++++++++++++ >>> 1 files changed, 26 insertions(+), 0 deletions(-) >>> >>> diff --git a/include/linux/bug.h b/include/linux/bug.h >>> index 1b43ea2..91bd9d5 100644 >>> --- a/include/linux/bug.h >>> +++ b/include/linux/bug.h >>> @@ -16,6 +16,7 @@ struct pt_regs; >>> #define BUILD_BUG_ON_NOT_POWER_OF_2(n) >>> #define BUILD_BUG_ON_ZERO(e) (0) >>> #define BUILD_BUG_ON_NULL(e) ((void*)0) >>> +#define BUILD_BUG_ON_MSG(cond, msg) (0) >>> #define BUILD_BUG_ON(condition) (0) >>> #define BUILD_BUG() (0) >>> #else /* __CHECKER__ */ >>> @@ -38,6 +39,31 @@ struct pt_regs; >>> */ >>> #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) >>> >>> +#define _CONCAT1(a, b) a##b >>> +#define CONCAT(a, b) _CONCAT1(a, b) >> >> Let's call the indirection _CONCAT without the "1". No problem, naming conventions are good! :) >> >>> +#define UNIQUIFY(prefix) CONCAT(prefix, __LINE__) >>> + >>> +#define BUILD_BUG_INTERNAL2(condition, msg, fn) \ >>> + do { \ >>> + extern void fn (void) __compiletime_error(msg); \ >>> + __compiletime_error_fallback(condition); \ >>> + if (condition) \ >>> + fn(); \ >>> + } while (0) >>> + >>> +#define BUILD_BUG_INTERNAL(condition, msg, fn) \ >>> + BUILD_BUG_INTERNAL2(condition, msg, fn) >> >> Ditto. BUILD_BUG_INTERNAL2 should be __BUILD_BUG_INTERNAL and the one >> calling it _BUILD_BUG_INTERNAL (with one underscore). > > Also, you don't need both the BUILD_BUG_INTERNAL and CONCAT/UNIQUIFY > macros. My original implementation just used the BUILD_BUG_INTERNAL > family of macros; if you'd rather rename them, by all means do so, but I > don't think you need two separate families of multiply-indirect macros. Yeah, I was thinking in terms of reusable macros. I'm kinda thinking the kernel needs a header just for handy little macros, like concat, uniquify, the IS_EMPTY and IF_EMPTY macros of mine in rbtree.h, etc. There is a stringify.h that just contains a __stringify macro. But here, it's just verbose, so I'll change it back to how you had it. >>> + >>> +/** >>> + * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied >>> + * error message. >>> + * @condition: the condition which the compiler should know is false. >>> + * >>> + * See BUILD_BUG_ON for description. >>> + */ >>> +#define BUILD_BUG_ON_MSG(cond, msg) \ >>> + BUILD_BUG_INTERNAL(cond, msg, UNIQUIFY(__build_bug_on_failed_)) >> >> Btw, why are we adding the line at all? It is issued by gcc anyway: >> >> cc -Wall macros.c -o macros >> macros.c: In function ‘main’: >> macros.c:22:1: error: ‘__build_bug_on_failed_22’ undeclared (first use in this function) > > Because without that, you end up writing multiple prototypes for the > same function (__build_bug_on_failed) with different error attributes, > and GCC will ignore all but the last error attribute it sees, even with > a scoped prototype. Yeah, this is part of the trick to get non-existent functions with different messages on their error attributes, so that each BUILD_BUG_ON-type macro can have more helpful text in its error message. I don't know what's in your macros.c, but it should have given you a much more shiny error message. Daniel