[Buildroot] nios2 : gcc 4.9.x buildroot toolchain broken

On 2 August 2015 at 02:48, Chung-Lin Tang [off-list ref] wrote:

On 2015/8/2 12:08 AM, Ezequiel Garcia wrote:

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On 07/27/2015 05:48 PM, Thomas Petazzoni wrote:

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Dear Brendan Heading,

Hi Brendan,

Thanks a lot for the report.

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On Mon, 27 Jul 2015 21:28:21 +0100, Brendan Heading wrote:

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While looking at the dmraid build bug on nios2 I noted that it is not
possible to build a buildroot toolchain based on GCC 4.9.x for that
platform.

You can reproduce the problem using the following (one-line) defconfig :

BR2_nios2=y

I tested it against the commit : 5ccde01652bc41da325bf4c9a5abbf0031080784

The error is as follows :

=============
../../../libgcc/config/nios2/linux-atomic.c:23:24: fatal error:
asm/unistd.h: No such file or directory
  #include <asm/unistd.h>
                         ^
compilation terminated.
=============

The problem only occurs on GCC 4.9.x. GCC 5.x builds fine.

Someone already submitted a patch to fix this :

http://lists.busybox.net/pipermail/buildroot/2015-February/119084.html

The submitter promised to do some more work but it seems to have been left
that way since last February.

Not entirely true :-) I actually did re-submit the patch later,
together with the rest of the internal toolchain support (as was
requested):

http://patchwork.ozlabs.org/patch/440651/

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We can either :
- disable GCC 4.9.x for nios2 (leaving 5.x as the only supported buildroot
toolchain)
- integrate & test the above patch

What does everyone think ? Given that the above patch seems to be
considered incomplete maybe we should disable nios2 4.9.x for now until the
required additions have been submitted.

Hum, that's interesting. I indeed saw that gcc 4.9.3 was not building
properly for NIOS II. However, gcc 4.9.2 built fine for me. Look at
http://autobuild.buildroot.org/toolchains/tarballs/br-nios2-full-2015.05.tar.bz2:
it is a NIOS II gcc 4.9.2 toolchain generated by Buildroot.

So I don't really understand how Ezequiel fall into the problem of
<asm/unistd.h> with gcc 4.9.2. But I did indeed fall into this problem
with gcc 4.9.3.

Hope I'm not being nonsense (it's been a while since February and I
haven't touched my nios2), but maybe you didn't fall because you had
my patch applied when you built that toolchain?

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Or maybe the problem is *not* gcc version related only, but also
related to the kernel headers version?

Looking through the rest of the architectures, the only
ones that have any non-local includes are m68k and nios2:

$ find libgcc/config/ -name *atomic.c
libgcc/config/nios2/linux-atomic.c
libgcc/config/tilepro/atomic.c
libgcc/config/sh/linux-atomic.c
libgcc/config/m68k/linux-atomic.c
libgcc/config/arm/linux-atomic.c
libgcc/config/pa/linux-atomic.c

$ find libgcc/config/ -name *atomic.c | xargs grep "include <"
libgcc/config/nios2/linux-atomic.c:#include <asm/unistd.h>
libgcc/config/m68k/linux-atomic.c:#include <asm/unistd.h>
libgcc/config/m68k/linux-atomic.c:#include <stdbool.h>

The rest don't include anything, so I'd guess it's gcc what's wrong.
I don't know much about gcc, so it's really just a guess.

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But in any case, Ezequiel's patch seems fine to me, I'll try to apply
something similar.

And maybe the GCC maintainers can manage to include this change
in future releases (Ccing Chung-Lin Tang).

I recently committed the patch to remove the '#include <asm/unistd.h>' line
to upstream 5.x, 4.9.x branches, though it's not in 4.9.3.
You can get it immediately if there's an option in buildroot to checkout
stable branches of upstream GCC (as opposed to only released tarballs)

That's great! thanks for the update,
-- 
Ezequiel Garc?a, VanguardiaSur
www.vanguardiasur.com.ar