[OE-core] [PATCH] boost: Convert ??= weaker assingment to weak ?= assignment

[Khem Raj]

On Thursday, January 23, 2014 09:31:47 AM Chris Larson wrote:
> On Wed, Jan 22, 2014 at 6:16 PM, Khem Raj <raj.khem at gmail.com> wrote:
> > On Friday, December 06, 2013 05:42:26 PM Khem Raj wrote:
> > > ??= does not react at all with
> > > BOOST_LIBS += "${@base_contains('PACKAGECONFIG', 'python', 'python', '',
> > > d)}"
> > > 
> > > even though we have
> > > 
> > > PACKAGECONFIG ??= "" it does not honor it and always add python to
> > > BOOST_LIBS but the dependency is not added so it fails to build
> > > complaining for missing python headers which is a understood outcome
> > > 
> > > When converted to ?= it works as expected and only add --with-python
> > > in bjam when python is specified in PACKAGECONFIG otherwise not.
> > > 
> > > Is it a bitbake bug ? in anycase ?= should be enough of loose rope
> > > to let user/distro configure the packageconfig policy
> > 
> > OK so the problem is that I have meta-ros in my layer-mix and in that
> > layer
> > it defines PACKAGECONFIG ?= "python" IMO it should have appended instead
> > of
> > redefining. Thats why I was seeing what I was seeing.
> 
> It's worth noting that recipes, in general, should use ?= rather than ??=,
> but config files, in general, should use ??=. Otherwise it becomes
> impossible for the config metadata to define an overriding default -- the
> last ??= wins, after all, and that would always be the recipe. IMO default
> values in the recipe are there to give sane behavior when there's no
> configuration coming in from elsewhere, not to override configuration
> defaults.

yes I think thats a good point. so lets consider this patch for inclusion
now we know the reason, I can resubmit with proper subject and patch header

-- 
-Khem
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