Re: [PATCH] ARM: Blacklist GCC 4.8.0 to GCC 4.8.2 - PR58854

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Fri, Oct 17, 2014 at 02:41:12PM +0100, Russell King - ARM Linux wrote:
> On Thu, Oct 16, 2014 at 10:58:06AM -0400, Nicolas Pitre wrote:
> > On Thu, 16 Oct 2014, Russell King - ARM Linux wrote:
> > 
> > > So, let me put this another way: a compiler with this bug is _completely_
> > > unsuitable for use for compiling programs for use under the Linux
> > > kernel _as well_ as the Linux kernel itself.
> > > 
> > > The difference is that the Linaro compilers come with an expectation
> > > that they are usable on ARM... whereas stock versions cover a lot more
> > > and so the ARM arch is probably very small number of their users.
> > > 
> > > Hence why I recommend that Linaro takes down their buggy compiler.
> > > Their 4.8.3 version should not be used *anywhere*, just the same as
> > > the stock 4.8 to 4.8.2 inclusive should also not be used anywhere on
> > > ARM either.
> > 
> > Here's the answer from the toolchain team:
> > 
> > On Thu, 16 Oct 2014, Yvan Roux <yvan.roux@linaro.org> wrote:
> > 
> > | Hi Nicolas,
> > |
> > | thanks for bringing this to our knowledge.
> > |
> > | The fix for PR58854 was included in our releases since the GCC
> > | 4.8-2013.12 which is based on a 4.8.3 prerelease version (at svn
> > | revision 205577).  As we are doing monthly releases based on a
> > | revision of the related FSF branch, using GCC_VERSION (__GNUC__,
> > | __GNUC_MINOR,__GNUC_PATCHLEVEL) is not accurate enough to identify the
> > | release version (all our releases between November 2013 and May 2014
> > | will be 4.8.3) the __VERSION__ predefined macro is a bit more accurate
> > | here ("4.8.3 20131202 (prerelease)") but not completely satisfactory.
> > |
> > | I completely agree that we should at least mention in our impacted
> > | releases download pages that this bug is present.
> 
> Unfortunately, __VERSION__ doesn't help us identify that the bug has
> been fixed - it's not something which can be tested at preprocessor
> time.
> 
> Those which identify themselves as 4.8.3 won't be impacted by the patch,
> which means that the Linaro 4.8.3 GCC versions will continue to build
> the kernel just fine.  Even the buggy versions.
> 
> I don't see the point of continuing to offer the buggy versions for
> download though - the compiler is totally unsuitable for building any
> Linux related binaries, be that kernel or userspace, and so should not
> be used under any circumstances, period.

Right, with the test fixed (&& instead of ||), I've just pushed it out
this morning, and received the results from Olof's kernel builder,
which shows that he's using a gcc 4.8.x version which gets caught by
the test.

I think Olof needs to do something about his gcc version there.

-- 
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.