From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757436AbXKNC4R (ORCPT ); Tue, 13 Nov 2007 21:56:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754507AbXKNC4C (ORCPT ); Tue, 13 Nov 2007 21:56:02 -0500 Received: from smtp2.linux-foundation.org ([207.189.120.14]:41714 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753734AbXKNC4A (ORCPT ); Tue, 13 Nov 2007 21:56:00 -0500 Date: Tue, 13 Nov 2007 18:55:26 -0800 (PST) From: Linus Torvalds To: Joe Perches cc: linux-kernel Subject: Re: [PATCH] - [12/15] - remove defconfig ptr comparisons to 0 - include/asm-x86 In-Reply-To: <1195005932.5163.98.camel@localhost> Message-ID: References: <1195005932.5163.98.camel@localhost> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 Nov 2007, Joe Perches wrote: > > Remove defconfig ptr comparison to 0 > > The memcpy from memory location 0 sure looks odd. Btw, this is also very compiler-bug-prone. And sadly, the cast to "(void *)" doesn't help. This could easily be a case where a compiler decides to play lawyer games, knowing that "NULL pointers cannot be dereferenced", deciding that it's all totally undefined behavior, and then just "optimizing" it all away. > - memcpy(&header, 0, sizeof(struct acpi_table_header)); > + memcpy(&header, (void *)0, sizeof(struct acpi_table_header)); So to be safe from bogus compilers who care more about standards than the obvious intention of the programmer, it might actually be better in the long run to do something like static inline void *create_pointer(unsigned long val) { void *result; asm("":"=r" (result):"0" (val)); return result; } and then use "create_pointer(0)" here. On that note: I'm not going to apply this series, because it's simply not really appropriate any more. But when re-sending for 2.6.25-rc1, can you make the subject lines have a slightly higher signal-to-noise ratio, ie dropt he unnecessary stuff that doesn't add any value as a commit message (eg "defconfig"? Is it really relevant?), and make it properly formatted? My scripts by default remove the stuff in between []'s, so the end result for the commit message header from this subject line would be "- remove defconfig ptr comparisons to 0 - include/asm-x86" which is strange and not very useful. It would read better as Subject: [PATCH 1/15] include/asm-x86: remove ptr comparisons to 0 which would create a commit message header that is more readable. Linus