[oe] USE flags mumbling

[Martin Jansa]

On Thu, Jul 01, 2010 at 03:22:54PM -0700, Tom Rini wrote:
> I wonder, and I have to admit to having no real gentoo background
> here, how do they solve this problem?  Did they invent their own
> package format and add another field that consists of use flags?
> That'd make some stuff a lot easier, but making deb/rpm get that
> mapping somehow seems hard at first.

They store all information about built packages in
/var/db/pkg/category/name/*

So they know which USE flags were ON and OFF when you built it, there is
also environment.bz2 where you can find which gcc version was used to
build it.

So it's easy to rebuild all installed packages if current systems
settings gives different USE flag sets then before (--newuse param) or
with small script I used to rebuild all remaining packages which weren't
rebuild after system gcc upgrade.

Lately (imho with new EAPI) they can also narrow dependencies not only
with requested version, but also with some USE flag ON or OFF.

And they have it much easier as they resolve it on target device, to
provide --newuse functionality in OE we would probably do PR bump of
all "changed" recipes.

So in the end it will be far from ideal if we try just to encode "our" USE
flags to ${PN}. 

Regards,

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa at gmail.com