[oe] USE flags mumbling

[Tom Rini]

Graeme Gregory wrote:
> We already have BBCLASSEXTENDS which modifies ${PN} of a package and
> can use overrides to change behaviors of recipes.
> 
> Maybe USE flags could be implemented in a similar fashing.
> 
> DISTRO_USE = "nossl nox11"
> 
> EXTRA_OECONF_append_use-nossl = "--disable-ssl"
> 
> ${PN} of the recipe becomes XXXX-nossl
> 
> Thoughts?

First we'd have to have a discussion on what the default should be and 
get agreement everywhere (ssl? x11? bluetooth (bluez3? bluez4?)? alsa?) 
on the whole raft of things that it would be nice to globally turn off 
or on.  Then we have to know which ones a given recipe actually made use 
of as opkg-nox11 is quite silly but conversely it'd be quite nice to 
have in autotools.bbclass the magic to always pass --disable-x11 (since 
it sure feels like everyone uses the same enable/disable switch finally).

Second, we also need a raft of, and perhaps a much easier way to, add 
binary package output virtuals.

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.

-- 
Tom Rini
Mentor Graphics Corporation