[OE-core] How to find out why my do_compile depends on $MACHINE

[Mike Looijmans]

On 05-10-15 15:22, Richard Purdie wrote:
> On Mon, 2015-10-05 at 13:49 +0200, Mike Looijmans wrote:
>> On 05-10-15 12:18, Richard Purdie wrote:
>>> On Mon, 2015-10-05 at 11:34 +0200, Mike Looijmans wrote:
...
>> For the bigger picture:
>>
>> If I have a recipe that says:
>>
>> X = "x"
>>
>> And I refactor it a bit to read:
>>
>> Y = "x"
>> X = "${Y}"
>>
>> What is the logic behind having to rebuild the package now? Why does the
>> 'source' of the contents matter to the hash? It won't generate different
>> output, regardless whether X is 'calculated' or just 'constant'.
>>
>> In particular, I've noticed this happening when switching between AUTOREV and
>> a fixed revision in a recipe.
>
> This is simply just the way the system is designed. It checksums the
> intermediate steps as well as the endpoints. I guess in the above
> example the system might do "export Y" for example.

In that case, "Y" would end up in the package's sstate hash, and hence it 
would rebuild when Y changes.

I have a workaround now, multiple workarounds actually, but I'm trying to 
understand why the system would be designed this way. Currently I'm tempted to 
splatter X[vardepvalue]="${X}" all over the place just to get rid of this 
annoying behaviour.

> There are alternative ways to do things but its simply not the way
> things were implemented. If you do need to collapse the dependency
> chain, you can use vardepvalue which was added for that reason. There
> are only a small number of places you really need to do that.

Lets make things more concrete. My distro.conf now reads:

FULL_OPTIMIZATION = "-O2 -pipe ${DEBUG_FLAGS}"

Say I want to build packages with varying optimization levels. I consider 
myself pretty smart, so in this distro.conf file, I change that line to:

OPT_LEVEL ?= "-O2"
FULL_OPTIMIZATION = "${OPT_LEVEL} -pipe ${DEBUG_FLAGS}"

So now I can replace the optimization level of some packages by simply 
changing the OPT_LEVEL variable.

Nice, but this will trigger a rebuild of ALL packages, event though the build 
flags did not change at all!

I can't think of any reason why this would be desirable. Why is it designed 
this way?



Kind regards,

Mike Looijmans
System Expert

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