Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757435Ab2JEVDO (ORCPT ); Fri, 5 Oct 2012 17:03:14 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:38872 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754118Ab2JEVDI convert rfc822-to-8bit (ORCPT ); Fri, 5 Oct 2012 17:03:08 -0400 X-Originating-IP: 217.70.178.138 X-Originating-IP: 173.246.103.110 Date: Fri, 5 Oct 2012 14:02:59 -0700 From: Josh Triplett To: Borislav Petkov , danielfsantos@att.net, 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} Message-ID: <20121005210258.GB7362@jtriplet-mobl1> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20121005205858.GB28452@liondog.tnic> User-Agent: Mutt/1.5.21 (2010-09-15) Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3329 Lines: 83 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". > > > +#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. > > + > > +/** > > + * 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. - Josh Triplett -- 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/