what is the value of 'BBPATH ?= ""' in layer.conf?

what is the value of 'BBPATH ?= ""' in layer.conf?

[Robert P. J. Day]

  perusing some wind river layers, and in the layer.conf file here:

https://github.com/WindRiver-OpenSourceLabs/wr-kernel/blob/LB21_7.0_RCPL0002/conf/layer.conf

i see the opening snippet:

  BBPATH ?= ""
  # We have a conf and classes directory, add to BBPATH
  BBPATH := "${LAYERDIR}:${BBPATH}"

what is the purpose of that initial assignment

  BBPATH ?= ""

if that variable has no value, won't it just expand to the empty
string so that the eventual effect is the same? or is there something
more subtle happening here?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: what is the value of 'BBPATH ?= ""' in layer.conf?

[Robert Yang]

On 11/22/2015 05:10 PM, Robert P. J. Day wrote:
>
>    perusing some wind river layers, and in the layer.conf file here:
>
> https://github.com/WindRiver-OpenSourceLabs/wr-kernel/blob/LB21_7.0_RCPL0002/conf/layer.conf
>
> i see the opening snippet:
>
>    BBPATH ?= ""
>    # We have a conf and classes directory, add to BBPATH
>    BBPATH := "${LAYERDIR}:${BBPATH}"
>
> what is the purpose of that initial assignment
>
>    BBPATH ?= ""

There would be a warning when BBPATH is null, but that had been fixed,
so we don't need it nowadays.

// Robert

>
> if that variable has no value, won't it just expand to the empty
> string so that the eventual effect is the same? or is there something
> more subtle happening here?
>
> rday
>

Re: what is the value of 'BBPATH ?= ""' in layer.conf?

[Robert P. J. Day]

On Sun, 22 Nov 2015, Robert Yang wrote:

>
>
> On 11/22/2015 05:10 PM, Robert P. J. Day wrote:
> >
> >    perusing some wind river layers, and in the layer.conf file here:
> >
> > https://github.com/WindRiver-OpenSourceLabs/wr-kernel/blob/LB21_7.0_RCPL0002/conf/layer.conf
> >
> > i see the opening snippet:
> >
> >    BBPATH ?= ""
> >    # We have a conf and classes directory, add to BBPATH
> >    BBPATH := "${LAYERDIR}:${BBPATH}"
> >
> > what is the purpose of that initial assignment
> >
> >    BBPATH ?= ""
>
> There would be a warning when BBPATH is null, but that had been fixed,
> so we don't need it nowadays.
>
> // Robert

  i thought as much, i just wanted to be sure. i am a rabid minimalist
in that, if a line has no value, it should be removed, mostly to avoid
confusing people like me. :-) i noticed at least a couple WR-OSL
layers that had that construct, you can decide if you care enough
about it to clean it up. thanks for the clarifiation.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: what is the value of 'BBPATH ?= ""' in layer.conf?

[Robert Yang]

On 11/22/2015 05:29 PM, Robert P. J. Day wrote:
> On Sun, 22 Nov 2015, Robert Yang wrote:
>
>>
>>
>> On 11/22/2015 05:10 PM, Robert P. J. Day wrote:
>>>
>>>     perusing some wind river layers, and in the layer.conf file here:
>>>
>>> https://github.com/WindRiver-OpenSourceLabs/wr-kernel/blob/LB21_7.0_RCPL0002/conf/layer.conf
>>>
>>> i see the opening snippet:
>>>
>>>     BBPATH ?= ""
>>>     # We have a conf and classes directory, add to BBPATH
>>>     BBPATH := "${LAYERDIR}:${BBPATH}"
>>>
>>> what is the purpose of that initial assignment
>>>
>>>     BBPATH ?= ""
>>
>> There would be a warning when BBPATH is null, but that had been fixed,
>> so we don't need it nowadays.
>>
>> // Robert
>
>    i thought as much, i just wanted to be sure. i am a rabid minimalist
> in that, if a line has no value, it should be removed, mostly to avoid
> confusing people like me. :-) i noticed at least a couple WR-OSL
> layers that had that construct, you can decide if you care enough
> about it to clean it up. thanks for the clarifiation.

Thanks, we have cleaned that up in new release.

// Robert

>
> rday
>

Re: what is the value of 'BBPATH ?= ""' in layer.conf?

[Mark Hatle]

On 11/22/15 3:10 AM, Robert P. J. Day wrote:
> 
>   perusing some wind river layers, and in the layer.conf file here:
> 
> https://github.com/WindRiver-OpenSourceLabs/wr-kernel/blob/LB21_7.0_RCPL0002/conf/layer.conf
> 
> i see the opening snippet:
> 
>   BBPATH ?= ""
>   # We have a conf and classes directory, add to BBPATH
>   BBPATH := "${LAYERDIR}:${BBPATH}"

(for the -first- layer defined)

BBPATH := "${LAYERDIR}:${BBPATH}"

will result in a warning or error because the ${BBPATH} can't be expanded.

There was a commit late 2013 to OE-Core and most related layers that turned this
into a append (or in this case prepend):

BBPATH =. "${LAYERDIR}:"

This is stop the need for the BBPATH and work properly.

LAYERDIR is always expanded when used, so no need for the :=

--Mark

> what is the purpose of that initial assignment
> 
>   BBPATH ?= ""
> 
> if that variable has no value, won't it just expand to the empty
> string so that the eventual effect is the same? or is there something
> more subtle happening here?
> 
> rday
>