From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751778AbXHUTzi (ORCPT ); Tue, 21 Aug 2007 15:55:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750811AbXHUTza (ORCPT ); Tue, 21 Aug 2007 15:55:30 -0400 Received: from mailout.stusta.mhn.de ([141.84.69.5]:53439 "EHLO mailhub.stusta.mhn.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750716AbXHUTz3 (ORCPT ); Tue, 21 Aug 2007 15:55:29 -0400 Date: Tue, 21 Aug 2007 21:54:33 +0200 From: Adrian Bunk To: Andi Kleen Cc: Randy Dunlap , Linus Torvalds , Andrew Morton , Jarek Poplawski , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: RFC: drop support for gcc < 4.0 Message-ID: <20070821195433.GE30705@stusta.de> References: <20070821132038.GA22254@ff.dom.local> <20070821093103.3c097d4a.randy.dunlap@oracle.com> <20070821173550.GC30705@stusta.de> <20070821191959.GC2642@bingen.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20070821191959.GC2642@bingen.suse.de> User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 21, 2007 at 09:19:59PM +0200, Andi Kleen wrote: > On Tue, Aug 21, 2007 at 07:35:50PM +0200, Adrian Bunk wrote: > > Obviously a gcc <= 3.4 [1], and therefore no unit-at-a-time. > > Actually there are widely used 3.3 variants that support unit-at-a-time > (e.g. 3.3-hammer which was shipped by several distributions for some time) > > There are still a lot of systems around which use gcc 3.3 (less so with > 3.4). Unless there's a major bug that is hard to work around I would > prefer to keep it supported. > > Bogus warnings should be relatively harmless. How many kernel developers use such old gcc versions? And how many people notice the valid modpost warnings that can indicate a runtime Oops? > > And it's becoming a real maintainance problem that not only this problem > > but also other problems like some section mismatches [2] are only > > present without unit-at-a-time. > > The unit-at-a-time output order is not defined, so even if it works > with the current compiler a compiler change might still trigger > that problem. So it would be better to fix those anyways. The example [2] from my email is guaranteed to not be a problem with unit-at-a-time (as long as unit-at-a-time implies inline-functions-called-once - and that's although theoretically possible quite unlikely to change in practice). This example is for a bug that should be fixed, but my point is the maintainability, IOW: issues with older compilers might not be discovered and fixed before they go into a stable kernel. We currently support 6 different stable gcc release series plus heavily modified vendor branches like 3.3-hammer. We can discuss whether it is now already the right time, and where to make the cut, but medium-term we must reduce the number of supported compilers. > -Andi cu Adrian [2] example: static __init function with exactly one caller, and this caller is non-__init -- "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