[OE-core] RFC: Separate build dir for autotools

[Khem Raj]

On Mon, Feb 24, 2014 at 6:58 AM, Richard Purdie
<richard.purdie at linuxfoundation.org> wrote:
> For a while poky and others have been using the seperatebuilddir.inc
> file. This makes ${S} != ${B} and means that ${B} can be wiped when
> configuration changes.
>
> This helps deal with the fact that autotools and friends are not
> particular good at rebuilding things that change. The recent libcheck
> upgrade which broke bluez4 builds is but one example of the kind of
> problem we can hit. Sadly bluez4 doesn't work for S!=B so it didn't
> protect against that issue but it does protect other packages.
>
> I'd really love to switch the default in autotools.bbclass to make this
> the default and then have broken packages opt out of it.
>
> I can deal with OE-Core and make sure the metadata there is updated, my
> bigger worry is what this would do to other layers.
>
> The options I can see are therefore basically:
>
> a) We change the default in autotools.bbclass and fix things that break

This would be sort of late call for 1.6 IMO but I would prefer this solution.

>
> b) We introduce an "autotools2" class and have recipes inherit that.
> This version would default to separate builddirs. It does mean change to
> all the "good" recipes rather than the broken ones though and hence a
> fair bit of churn.

probably a better migration path can happen over time. may be we can raname
existing autotools.bbclass to autotoolsold and have autotools.bbclass
default to S != B
that way the recipes which break can inherit autotoolsold and can have quick fix
then we can slowly remove inheriting autotoolsold and finally remove
the class itself.

>
> Have we got the willpower to fix a)? is b) an option? Other ideas?
>
> One way or another I think we should try and switch things somehow...
>
> Cheers,
>
> Richard
>
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