[Buildroot] [RFCv1 3/4] toolchain: post-pone evaluation of TOOLCHAIN_EXTERNAL_BIN

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

Hello,

On Tue, 7 Nov 2017 22:23:24 +0100, Arnout Vandecappelle wrote:

> > diff --git a/toolchain/toolchain-external/pkg-toolchain-external.mk b/toolchain/toolchain-external/pkg-toolchain-external.mk
> > index dc0588c536..b9ad1720a1 100644
> > --- a/toolchain/toolchain-external/pkg-toolchain-external.mk
> > +++ b/toolchain/toolchain-external/pkg-toolchain-external.mk
> > @@ -77,7 +77,7 @@ ifneq ($(TOOLCHAIN_EXTERNAL_PREFIX),)
> >  TOOLCHAIN_EXTERNAL_BIN := $(dir $(shell which $(TOOLCHAIN_EXTERNAL_PREFIX)-gcc))
> >  endif
> >  else
> > -TOOLCHAIN_EXTERNAL_BIN := $(TOOLCHAIN_EXTERNAL_INSTALL_DIR)/bin
> > +TOOLCHAIN_EXTERNAL_BIN = $(TOOLCHAIN_EXTERNAL_INSTALL_DIR)/bin  
> 
>  It gives me the shivers to see the same variable sometimes defined recursive
> and sometimes defined immediate... But I can't find an elegant solution (other
> than introducing an artificial extra variable, which is also ugly), so
> 
> Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

I also saw the other TOOLCHAIN_EXTERNAL_BIN assignment using := above,
and didn't change it for now because that was not the case I was
interested in testing/fixing. But my plan was to get back to this :=
assignment at some point. However, it seems like you have concluded
that we have to keep := here. Could you explain why?

Note: I think keeping the := is OK, because TOOLCHAIN_EXTERNAL_PREFIX
doesn't reference anything like HOST_DIR/STAGING_DIR/TARGET_DIR, so
it's fine to have evaluation at the time of assignment for this case.

Perhaps a comment above would help clarify that it's intentional?

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