[Buildroot] [PATCH] package/protobuf: uses fork(), not available on no-MMU platforms

[Thomas Petazzoni]

Hello,

On Sat, 27 Aug 2016 02:17:03 +0200, Jörg Krause wrote:
> Propagate the dependency to the packages mosh and ola.
> 
> Fixes:
> http://autobuild.buildroot.net/results/2c1/2c151e84d7854a810465dc16869023e0ada2d586/
> 
> Signed-off-by: Jörg Krause <joerg.krause at embedded.rocks>

At first, I was a bit surprised as to why we're seeing this only now,
so I investigated a bit, and came to the following conclusion, which I
added to the commit log:

"""
    This was not noticed until now because:
    
     1/ The older Blackfin toolchain doesn't have libatomic, so it didn't
        provide the atomic operations that protobuf needs, so protobuf was
        never built.
    
     2/ The ARM Cortex-M toolchain is static-only, and protobuf requires
        dynamic library support.
    
    So it's only with the new Blackfin toolchain, which is based on gcc
    6.x (and therefore provides libatomic) and is FDPIC-based (and therefore
    has dynamic library support) that this problem appeared.

"""


> diff --git a/package/protobuf/Config.in b/package/protobuf/Config.in
> index 3215a07..4a8d1ef 100644
> --- a/package/protobuf/Config.in
> +++ b/package/protobuf/Config.in
> @@ -33,6 +33,7 @@ config BR2_PACKAGE_PROTOBUF
>  	depends on BR2_INSTALL_LIBSTDCPP
>  	depends on BR2_TOOLCHAIN_HAS_THREADS
>  	depends on BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS
> +	depends on BR2_USE_MMU # fork()
>  	depends on !BR2_STATIC_LIBS
>  	help
>  	  Protocol buffers are Google's language-neutral, platform-neutral,

When you add a new dependency, you must also propagate it to the
Config.in comment so that those comments don't appear on no-MMU
platforms.

*However*, in this specific case, there was already a
BR2_PACKAGE_PROTOBUF_ARCH_SUPPORTS, to which it makes a lot of sense to
add the BR2_USE_MMU dependency: it's an architecture dependency, and by
doing so, it's automatically propagated to the existing comments and
reverse dependencies.

Applied with those changes. Thanks!

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