From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [RFC] minimum gcc version for kernel: raise to gcc-4.3 or 4.6? Date: Mon, 2 Jan 2017 12:23:47 +0000 Message-ID: <20170102122347.GB14217@n2100.armlinux.org.uk> References: <20161216105634.235457-1-arnd@arndb.de> <20161216170043.taaanbg5objnxjlh@breakpoint.cc> <2778134.jZdhGefl4B@wuerfel> <20161217112949.pghxlhdlxjzdumuo@mikejones.breakpoint.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20161217112949.pghxlhdlxjzdumuo@mikejones.breakpoint.cc> Sender: linux-kbuild-owner@vger.kernel.org To: Sebastian Andrzej Siewior Cc: Arnd Bergmann , linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org, kernel-build-reports@lists.linaro.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven , Andrew Morton , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@vger.kernel.org List-Id: linux-arch.vger.kernel.org On Sat, Dec 17, 2016 at 12:29:50PM +0100, Sebastian Andrzej Siewior wrote: > A new version is understandable. But why is an old version required? > One thing is an enterprise distro that is "current" or "supported" and still > stuck with gcc 4.1 because that is the version they decided to include in > their release. This is sad. But you might want to ask yourself why you want > the latest kernel but an old gcc / binutils. To help isolate changes. If you constantly upgrade everything, how do you bug hunt for a breakage? How do you know whether it's created by the kernel, or by (eg) a later version of gcc miscompiling the kernel. You have a large amount of code to start bug hunting through. Sticking with particular tool versions long-term means that you build up confidence in it - yes, sure, latent bugs exist, but it's easier to bug hunt if you aren't constantly suspecting that your tools might be broken. For example, I build kernels with: gcc binutils built on 32-bit ARM 4.7.4 2.25 April/May 2015 64-bit ARM 4.9.2 2.25.51.20150219 Feb/April 2015 I'm not anticipating upgrading them for some time yet - the only one which may get upgraded is the 64-bit binutils since later kernels now complain about a missing errata workaround in that toolchain version. I do still have some older toolchains around on some of my ARM boxes though, even a GCC 3 version with ARM TLS support for faster builds! -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pandora.armlinux.org.uk ([78.32.30.218]:35212 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbdABMX6 (ORCPT ); Mon, 2 Jan 2017 07:23:58 -0500 Date: Mon, 2 Jan 2017 12:23:47 +0000 From: Russell King - ARM Linux Subject: Re: [RFC] minimum gcc version for kernel: raise to gcc-4.3 or 4.6? Message-ID: <20170102122347.GB14217@n2100.armlinux.org.uk> References: <20161216105634.235457-1-arnd@arndb.de> <20161216170043.taaanbg5objnxjlh@breakpoint.cc> <2778134.jZdhGefl4B@wuerfel> <20161217112949.pghxlhdlxjzdumuo@mikejones.breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161217112949.pghxlhdlxjzdumuo@mikejones.breakpoint.cc> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Sebastian Andrzej Siewior Cc: Arnd Bergmann , linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org, kernel-build-reports@lists.linaro.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven , Andrew Morton , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@vger.kernel.org Message-ID: <20170102122347.MQX9KJCvGfdFJ-vKWjjjABjOJ5ePixItpxqYqpIB89c@z> On Sat, Dec 17, 2016 at 12:29:50PM +0100, Sebastian Andrzej Siewior wrote: > A new version is understandable. But why is an old version required? > One thing is an enterprise distro that is "current" or "supported" and still > stuck with gcc 4.1 because that is the version they decided to include in > their release. This is sad. But you might want to ask yourself why you want > the latest kernel but an old gcc / binutils. To help isolate changes. If you constantly upgrade everything, how do you bug hunt for a breakage? How do you know whether it's created by the kernel, or by (eg) a later version of gcc miscompiling the kernel. You have a large amount of code to start bug hunting through. Sticking with particular tool versions long-term means that you build up confidence in it - yes, sure, latent bugs exist, but it's easier to bug hunt if you aren't constantly suspecting that your tools might be broken. For example, I build kernels with: gcc binutils built on 32-bit ARM 4.7.4 2.25 April/May 2015 64-bit ARM 4.9.2 2.25.51.20150219 Feb/April 2015 I'm not anticipating upgrading them for some time yet - the only one which may get upgraded is the 64-bit binutils since later kernels now complain about a missing errata workaround in that toolchain version. I do still have some older toolchains around on some of my ARM boxes though, even a GCC 3 version with ARM TLS support for faster builds! -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.