Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753470AbWKCTIY (ORCPT ); Fri, 3 Nov 2006 14:08:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753473AbWKCTIY (ORCPT ); Fri, 3 Nov 2006 14:08:24 -0500 Received: from mailout.stusta.mhn.de ([141.84.69.5]:5138 "HELO mailout.stusta.mhn.de") by vger.kernel.org with SMTP id S1753470AbWKCTIX (ORCPT ); Fri, 3 Nov 2006 14:08:23 -0500 Date: Fri, 3 Nov 2006 20:08:24 +0100 From: Adrian Bunk To: Oleg Verych Cc: Mikulas Patocka , Andrew Morton , Gabriel C , LKML Subject: Re: New filesystem for Linux Message-ID: <20061103190824.GJ13381@stusta.de> References: <454A71EB.4000201@googlemail.com> <20061102174149.3578062d.akpm@osdl.org> <20061103171443.GA16912@flower.upol.cz> <20061103173609.GA17080@flower.upol.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061103173609.GA17080@flower.upol.cz> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1433 Lines: 48 On Fri, Nov 03, 2006 at 06:36:09PM +0100, Oleg Verych wrote: > On Fri, Nov 03, 2006 at 06:09:39PM +0100, Mikulas Patocka wrote: > > >In gmane.linux.kernel, you wrote: > > >[] > > >>From: Andrew Morton > > >> > > >>As Mikulas points out, (1 << anything) won't be evaluating to zero. > > > > > >How about integer overflow ? > > > > C standard defines that shifts by more bits than size of a type are > > undefined (in fact 1<<32 produces 1 on i386, because processor uses only 5 > > bits of a count). > ,-- > |#include > |int main(void) { > | unsigned int b = 1; > | > | printf("%u\n", (1 << 33)); > | printf("%u\n", (b << 33)); > | return 0; > |} > |$ gcc bit.c && ./a.out > `-- > > There *is* difference, isn't it? It's undefined, and the results with your example depend on the gcc version and optimization level. E.g. with gcc 4.1, there is *no* difference any more if you turn on optimization. cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed - 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/