From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] ARM: Blacklist GCC 4.8.0 to GCC 4.8.2 - PR58854 Date: Thu, 16 Oct 2014 15:29:44 +0100 Message-ID: <20141016142944.GR12379@n2100.arm.linux.org.uk> References: <063D6719AE5E284EB5DD2968C1650D6D1C9D80CC@AcuExch.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:35755 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751232AbaJPO37 (ORCPT ); Thu, 16 Oct 2014 10:29:59 -0400 Content-Disposition: inline In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1C9D80CC@AcuExch.aculab.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: David Laight Cc: Nathan Lynch , Peter Hurley , Otavio Salvador , Linus Torvalds , Nicolas Pitre , Linux OMAP Mailing List , "linux-arm-kernel@lists.infradead.org" On Thu, Oct 16, 2014 at 10:30:30AM +0000, David Laight wrote: > > +#ifdef __GNUC__ > > #if (__GNUC__ == 3 && __GNUC_MINOR__ < 3) > > #error Your compiler is too buggy; it is known to miscompile kernels. > > -#error Known good compilers: 3.3 > > +#error Known good compilers: 3.3, 4.x > > Except that isn't true since 4.8.0 isn't a good compiler. > > > +#endif > > +#if GCC_VERSION >= 40800 || GCC_VERSION < 40803 > > +#error Your compiler is too buggy; it is known to miscompile kernels > > +#error and result in filesystem corruption and oopses. > > +#endif > > #endif > > You are mixing the style of the version check. > Why not the single test: > #if GCC_VERSION < 30300 || (GCC_VERSION >= 40800 && GCC_VERSION < 40803) > #error Your compiler is too buggy; it is known to miscompile code. > #error Known good compilers: 3.3 onwards excluding 4.8.0 through 4.8.2 > #endif As you have just nicely demonstrated, changing what's already there can cause unintentional changes to creep in. The original test tested for GCC 3 compilers older than GCC 3.3, excluding GCC 2.96 and older. Your version blacklists everything before GCC 3.3. Such a change should be a separate patch. Moreover, if we really do want to blacklist all compilers older than GCC 3.3, then that too needs an explanation in the comments above this block, and in commit message. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net.