[Buildroot] [PATCH 04/20] package/skeleton: make SKELETON_LIB_SYMLINK a macro

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

Hello,

On Sat, 22 Jul 2017 14:56:19 +0200, Arnout Vandecappelle wrote:

> > +# Make a symlink lib32->lib or lib64->lib as appropriate.
> > +# MIPS64/n32 requires lib32 even though it's a 64-bit arch.
> > +# $(1): base dir (either staging or target)
> > +ifeq ($(BR2_ARCH_IS_64)$(BR2_MIPS_NABI32),y)  
> 
>  This makes me wonder: are we doing the right thing with NABI32? What is the
> semantics of BR2_ARCH_IS_64? I would say, it doesn't specify that you have a
> 32-bit or 64-bit capable CPU; instead, it says that you have a 32-bit or 64-bit
> userspace. I.e., that void* and long are 32 resp. 64 bits. Indeed, I don't think
> it's really relevant for Buildroot to know about the CPU capabilities, the
> important thing is the userpace ABI, i.e. how we compile packages.
> 
>  So, with that in mind, I think we should NOT select BR2_ARCH_IS_64 for the n32
> ABI. Similarly, when we add x32, it should also not be BR2_ARCH_IS_64.

I see your reasoning, but I believe it might be confusing to have
BR2_ARCH_IS_64 be false on a 64 bit architecture. However, we could
introduce something like BR2_UABI_IS_64, to define whether the
userspace ABI is 32 or 64 bits.

But doing that involves reviewing all the places where BR2_ARCH_IS_64
is used, and check if we're using it to say "the architecture is 64
bits" or "the userspace ABI is 32 bits".

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