[Buildroot] Analysis of build results for 2016-05-16

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello,

On Tue, 17 May 2016 11:56:07 -0700, Geoff Levand wrote:

> On Tue, 2016-05-17 at 15:36 +0200, Thomas Petazzoni wrote:
> >       x86_64 |                 flannel-v0.5.5 | NOK | http://autobuild.buildroot.net/results/6664189a6f3a815978e8d0a1d7ef408ca47e2874/
> > 
> > Geoff, can you look into this one?  
> 
> I believe I have the fix for this one in my patch 'package/go: Build
> special host binaries'.  This is a reworked version of what I posted
> last time.

OK.

> > >          arm |                  host-go-1.6.2 | NOK | http://autobuild.buildroot.net/results/42a8d07101d8d954511d1c884ecb66e8d861899e/  
> > 
> > error: #warning requested reentrant code
> > 
> > Geoff, in fact it seems like host-go itself needs thread support in the
> > target toolchain to build properly, so our plan to have only the Go
> > packages depend on BR2_TOOLCHAIN_HAS_THREADS does not work.  
> 
> Yes, the solution I came up with is that the go target package must

By "go target package", you mean a target package that is written in
Go, and not specifically the package/go/ package (which doesn't have a
target variant), right?

> specify BR2_TOOLCHAIN_HAS_THREADS if it uses cgo support.  If
> BR2_TOOLCHAIN_HAS_THREADS is set, then host-go sets CGO_ENABLED=1 and
> builds a compiler with cgo support.  If BR2_TOOLCHAIN_HAS_THREADS is
> not set, then host-go does not build in cgo support.  The two cases:
> 
> A go package which does not use cgo sets BR2_TOOLCHAIN_HAS_THREADS=n,

A package cannot *set* BR2_TOOLCHAIN_HAS_THREADS.
BR2_TOOLCHAIN_HAS_THREADS is a property of the toolchain.

> the host-go is not build with cgo support.  Both the target package
> and host-go should build OK since no thread support is needed.
> 
> A package that uses cgo sets BR2_TOOLCHAIN_HAS_THREADS=y, host-go
> is build with cgo support.  Both build OK since the toolchain has
> thread support.

What needs to happen instead is the following (and is quite similar to
what you said, except for the interaction with
BR2_TOOLCHAIN_HAS_THREADS=y) :

 *) The host-go package will build cgo support when
    BR2_TOOLCHAIN_HAS_THREADS=y and otherwise not build cgo support.

 *) Any target package that is written in Go and that needs cgo support
    should have a "depends on BR2_TOOLCHAIN_HAS_THREADS" in its
    dependencies.

This needs to be explained by a comment in package/go/go.mk, as it is
not trivial.

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com