[OE-core] OE-core] How do I find out why are packages being rebuilt?

[Mike Looijmans]

On 02/18/2013 12:11 PM, Burton, Ross wrote:
> On 18 February 2013 11:04, Mike Looijmans <mike.looijmans at topic.nl> wrote:
>> I'm still having trouble with packages being needlessly rebuilt over and
>> over. The worst of all it qt4-embedded, it takes about an hour to build.
>> This is wasting a LOT of time.
>>
>> The classic OE never rebuilt a package until its version changed.
>
> oe-core uses checksums of dependencies to determine what to rebuild -
> so if a class you inherit changes it's populate_packages_prepend()
> then the package task will re-execute, or if a dependeny package
> rebuilds then your package will rebuild too.  If you're tracking
> oe-core master then this often means large rebuilds as there may have
> been changes to the base.bbclass or package.bbclass which obviously
> impacts everything, and the usual churn in the packages.
>
> bitbake-diffsigs will let you follow the signature differences that
> cause a rebuild up the tree to identify what has changed.

Change in oe-core I can live with. Things that puzzle me are that when I 
change the location of a bootloader data file in my local.conf, it 
suddenly decides to rebuild qt4-embedded. I also have two almost 
identical machines (same cpu, same kernel, just a few different plugs), 
and I cannot figure out why it builds two separate qt4 binaries.

So I want to diagnose that. I have no idea where to start.