[OE-core] [RFC PATCH] bitbake.conf: Stop providing ${P} and ${PF} by default

[Chris Larson]

On Mon, Sep 9, 2013 at 7:14 AM, Richard Purdie <
richard.purdie at linuxfoundation.org> wrote:

> For a long time we've provided PN-PV and PN-PV-PR by tweaking PROVIDES.
> This looks
> nice at first glance however it turns out to be a bit problematic. Taking
> make as an
> example where there are two versions, 3.81 and 3.82, what should "bitbake
> make-3.81" do?
>
> Currently it builds make-3.81 and make-3.82 and breaks in interesting
> ways. Is that
> a bitbake bug? Well, it certainly shouldn't try and run the build. Why is
> it building
> 3.82 though? Its due to finding a dependency on "make-dev" and then trying
> to figure
> out what provides it? The answer is "make" and the default version of
> "make" is 3.82.
>
> So arguably, finding "make-3.81" should infer PREFERRED_VERSION_make =
> "3.81". Doing
> so resolved the above problem since now "make" resolves to "make-3.81".
>
> So what about if we have Recipe A:
> DEPENDS = "make-3.81"
> and Recipe B:
> DEPENDS = "make-3.82"
>
> That is clearly an error, easy. So finally what about if we have Recipe A:
> DEPENDS = "make-3.81"
> and Recipe B:
> DEPENDS = "make"
>
> The first recipe infers the PREFERRED_VERSION_make = "3.81" and then
> forces that
> version on everything else. Is that desired? Probably not in most cases,
> at least not
> silently.
>
> As mitigation, we could print a WARNING about this happening. The final
> part of the problem
> is that we can ony figure this out within bitbake itself. That means we'd
> have to teach bitbake
> about the PN-PV format of PROVIDES which is breaking the separation
> between bitbake and the
> metadata. We can't win :(.
>
> Nobody that I know of is using or relying on this functionality so perhaps
> we should
> just remove it instead which is what this patch does. Opinions?
>
> Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
>

This sounds like a good plan to me. We never *really* supported version
specific build dependencies anyway, and using those provides just caused
problems. Better for it to go away entirely.
-- 
Christopher Larson
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