Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757987Ab1DMUVh (ORCPT ); Wed, 13 Apr 2011 16:21:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41339 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757474Ab1DMUVf (ORCPT ); Wed, 13 Apr 2011 16:21:35 -0400 Date: Wed, 13 Apr 2011 22:20:31 +0200 From: Oleg Nesterov To: Andrew Morton Cc: Alexey Dobriyan , linux-kernel@vger.kernel.org, behlendorf1@llnl.gov Subject: Re: [PATCH] remove abs64() Message-ID: <20110413202031.GA19113@redhat.com> References: <20110412210045.GA19901@p183> <20110413142703.GA1511@redhat.com> <20110413114808.12783565.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110413114808.12783565.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1888 Lines: 60 On 04/13, Andrew Morton wrote: > > On Wed, 13 Apr 2011 16:27:03 +0200 > Oleg Nesterov wrote: > > > On 04/13, Alexey Dobriyan wrote: > > > > > > +#define abs(x) \ > > > +({ \ > > > + typeof(x) _x = (x); \ > > > + \ > > > + __builtin_choose_expr( \ > > > + __builtin_types_compatible_p(typeof(_x), signed char), \ > > > + (unsigned char)({ _x < 0 ? -_x : _x; }), \ > > > + __builtin_choose_expr( \ > > > + __builtin_types_compatible_p(typeof(_x), short), \ > > > + (unsigned short)({ _x < 0 ? -_x : _x; }), \ > > > + __builtin_choose_expr( \ > > > + __builtin_types_compatible_p(typeof(_x), int), \ > > > + (unsigned int)({ _x < 0 ? -_x : _x; }), \ > > > + __builtin_choose_expr( \ > > > + __builtin_types_compatible_p(typeof(_x), long), \ > > > + (unsigned long)({ _x < 0 ? -_x : _x; }), \ > > > + __builtin_choose_expr( \ > > > + __builtin_types_compatible_p(typeof(_x), long long), \ > > > + (unsigned long long)({ _x < 0 ? -_x : _x; }), \ > > > + _x))))); \ > > > +}) > > > > Personally I agree. > > > > But, we have some stupid users which do something like abs(u32_value) > > and expecting that abs() should treat this value as "signed". > > > > um, yes, I'd forgotten that one. That's a show-stopper. May be we can demand to fix them? I agree with Alexey, it is a bit ugly to have abs() and abs64(), and abs() itself doesn't look very nice. What if we simply add BUILD_BUG_ON( (typeof(_x)-1) > 0 ); into abs()? After that it would be trivial to find the offenders and fix them, - abs(unsigned_int) + abs((int) unsigned_int) Oleg. -- 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/