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[158.174.186.115]) by smtp.gmail.com with ESMTPSA id m17sm15000408lfj.22.2019.08.05.12.55.28 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 05 Aug 2019 12:55:29 -0700 (PDT) From: Rikard Falkeborn X-Google-Original-From: Rikard Falkeborn Date: Mon, 5 Aug 2019 21:55:26 +0200 To: Masahiro Yamada Cc: Rikard Falkeborn , Joe Perches , Andrew Morton , Johannes Berg , Linux Kernel Mailing List Subject: Re: [PATCH] linux/bits.h: Add compile time sanity check of GENMASK inputs Message-ID: <20190805195526.GA869@rikard> References: <20190731190309.19909-1-rikard.falkeborn@gmail.com> <47d29791addc075431737aff4b64531a668d4c1b.camel@perches.com> <2b782cf609330f53b6ecc5b75a8a4b49898483eb.camel@perches.com> <20190802181853.GA809@rikard> <20190803183637.GA831@rikard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 04, 2019 at 03:45:16PM +0900, Masahiro Yamada wrote: > On Sun, Aug 4, 2019 at 3:36 AM Rikard Falkeborn > wrote: > > > > On Sat, Aug 03, 2019 at 12:12:46PM +0900, Masahiro Yamada wrote: > > > On Sat, Aug 3, 2019 at 12:03 PM Masahiro Yamada > > > wrote: > > > > > > > > > > > BTW, v2 is already inconsistent. > > > > If you wanted GENMASK_INPUT_CHECK() to return 'unsigned long',, > > > > you would have to cast (low) > (high) as well: > > > > > > > > (unsigned long)((low) > (high)), UL(0)))) > > > > > > > > This is totally redundant, and weird. > > > > > > I take back this comment. > > > You added (unsigned long) to the beginning of this macro. > > > So, the type is consistent, but I believe all casts should be removed. > > > > Maybe you're right. BUILD_BUG_ON_ZERO returns size_t regardless of > > inputs. I was worried that on some platform, size_t would be larger than > > unsigned long (as far as I could see, the standard does not give any > > guarantees), and thus all of a sudden GENMASK would be 8 bytes instead > > of 4, but perhaps that is not a problem? > > > How about adding (int) cast to BUILD_BUG_ON_ZERO() ? I'll have a look.