Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753449AbYCLRUs (ORCPT ); Wed, 12 Mar 2008 13:20:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751644AbYCLRUj (ORCPT ); Wed, 12 Mar 2008 13:20:39 -0400 Received: from vs166246.vserver.de ([62.75.166.246]:39249 "EHLO vs166246.vserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbYCLRUi (ORCPT ); Wed, 12 Mar 2008 13:20:38 -0400 From: Michael Buesch To: Harvey Harrison Subject: Re: [PATCH 1/6] kernel: add clamp(), clamp_t() and clamp_val() macros Date: Wed, 12 Mar 2008 18:20:14 +0100 User-Agent: KMail/1.9.6 (enterprise 0.20070907.709405) Cc: Andrew Morton , LKML , Alan Cox , Jeff Garzik , Bartlomiej Zolnierkiewicz , Mauro Carvalho Chehab References: <1205269894.22317.32.camel@brick> <200803121613.09172.mb@bu3sch.de> <1205340866.8603.9.camel@brick> In-Reply-To: <1205340866.8603.9.camel@brick> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200803121820.14883.mb@bu3sch.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2797 Lines: 72 On Wednesday 12 March 2008 17:54:26 Harvey Harrison wrote: > On Wed, 2008-03-12 at 16:13 +0100, Michael Buesch wrote: > > So why not call it clamp_const()? > > One could even use __builtin_constant_p() and make clamp() use > > either clamp_const() or clamp_nonconst() from above automagically. > > I'd prefer that. > > Did you mean something like this? No more clamp_val, just clamp and > clamp_t. clamp_t forces all the types, clamp looks at the min and max > args, and if they are constants, uses the type of val instead. If not > a constant, the strict typechecking is done. > +#define clamp(val, min, max) ({ \ > + typeof(val) __val = (val); \ > + \ > + if (__builtin_constant_p(min)) { \ > + typeof(val) __min = (min); \ > + __val = __val < __min ? __min: __val; \ > + } else { \ > + typeof(min) __min = (min); \ > + (void) (&__val == &__min); \ > + __val = __val < __min ? __min: __val; \ > + } \ > + \ > + if (__builtin_constant_p(max)) { \ > + typeof(val) __max = (max); \ > + __val > __max ? __max: __val; \ > + } else { \ > + typeof(max) __max = (max); \ > + (void) (&__val == &__max); \ > + __val > __max ? __max: __val; \ > + } }) Yeah, something like that. Does returning of the value work over an indentation level, too? I dunno this detail of the language. But I'd prefer the following for readability anyway: + if (__builtin_constant_p(max)) { \ + typeof(val) __max = (max); \ + __val = __val > __max ? __max: __val; \ + } else { \ + typeof(max) __max = (max); \ + (void) (&__val == &__max); \ + __val = __val > __max ? __max: __val; \ + } + __val; }) Probably you can also only put the pointer check into the constant check: +#define clamp(val, min, max) ({ \ + typeof(val) __val = (val); \ + typeof(min) __min = (min); \ + typeof(max) __max = (max); \ + if (!__builtin_constant_p(min)) \ + (void) (&__val == &__min); \ + __val = __val < __min ? __min: __val; \ + if (!__builtin_constant_p(max)) \ + (void) (&__val == &__max); \ + __val = __val > __max ? __max: __val; \ + __val; }) But it seems that this evaluates the arguments twice, so my idea turns out to be not too good anyway. hm.. -- Greetings Michael. -- 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/