[Buildroot] [PATCH v3 5/6] package/flannel: Add BR2_TOOLCHAIN_HAS_THREADS

[Geoff Levand <geoff@infradead.org>]

Hi,

On Sat, 2016-05-28 at 15:41 +0200, Thomas Petazzoni wrote:
> There are still some issues with the flannel build:
> 
>   http://autobuild.buildroot.org/results/d98/d98e1857590738313a293b58f02230539bbaa405/build-end.log
> 
> The error is:
> 
> /home/buildroot/autobuild/run/instance-2/output/host/opt/ext-toolchain/bin/../lib/gcc/arm-buildroot-linux-uclibcgnueabi/4.9.3/../../../../arm-buildroot-linux-uclibcgnueabi/bin/ld: cannot find Scrt1.o: No such file or directory
> 
> My understanding is that this happens when trying to build PIE binaries
> that are statically linked. uClibc does not support that, or at least
> not with our current toolchain support. Would it be possible to not
> build PIE binaries with Go ? Or alternatively, investigate if it can be
> fixed in uClibc ?

Looking at the go sources, they force -pie when compiling cgo support
for ARM.  See line number 3188 in https://golang.org/src/cmd/go/build.go.

I think the only solution is to not build go packages that use cgo
when BR2_arm && BR2_TOOLCHAIN_USES_UCLIBC, so something like this:

+# cgo on ARM requires PIE linkage, which is not compatable with uClibc.
+comment "flannel is not available with uClibc-based toolchain on ARM architecture"
+       depends on BR2_PACKAGE_HOST_GO_ARCH_SUPPORTS
+       depends on BR2_TOOLCHAIN_HAS_THREADS
+       depends on BR2_arm && BR2_TOOLCHAIN_USES_UCLIBC
+
 config BR2_PACKAGE_FLANNEL
        bool "flannel"
        depends on BR2_PACKAGE_HOST_GO_ARCH_SUPPORTS
        depends on BR2_TOOLCHAIN_HAS_THREADS
+       depends on !(BR2_arm && BR2_TOOLCHAIN_USES_UCLIBC)
        help

If this looks OK, I'll submit a patch.

-Geoff