[OE-core] more pedantry -- looking to clarify layers definition, BBPATH, BBFILES, etc.

[Robert P. J. Day]

On Mon, 9 Jul 2012, Andrei Gherzan wrote:

>
> On Sun, Jul 8, 2012 at 8:59 PM, Robert P. J. Day <rpjday at crashcourse.ca> wrote:
>
>         (most of this is sort of self-evident but it's not documented as
>       well as it could be so i just want to make sure i have it exactly
>       right.)
>
>         snippets of some layer.conf files:
>
>       oe-core:
>
>       BBPATH .= ":${LAYERDIR}"
>       BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"
>
>       meta-hob:
>
>       BBPATH := "${BBPATH}:${LAYERDIR}"
>       BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb"
>
>       meta-yocto:
>
>       BBPATH := "${LAYERDIR}:${BBPATH}"
>       BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
>                   ${LAYERDIR}/recipes-*/*/*.bbappend"
>
>         note how meta-hob *appends* itself to BBPATH, while meta-yocto
>       *prepends* itself.  is there no possibility that this will cause some
>       confusion based on how BBPATH is used to resolve the location of class
>       or conf files?  i realize you should try to avoid that sort of
>       conflict but it still seems possible that someone might choose the
>       names of some files badly and the unpredictable ordering in BBPATH
>       will cause grief, no?
>
>
> I don't think this can cause any problems.

  are you sure?

> It's all about the order the files are searched. As long as you have
> proper priority set nothing can go wrong.

  but what if two or more layers have the same priority?  then what?
it may be that there's no issue here, i'm just pointing out the
possibility that, given the inconsistent way layers add themelves to
BBPATH (either prepending or appending) and the order one lists the
layers in bblayers.conf, is there absolutely no chance that someone
could experience unexpected behaviour given an unusual combination of
circumstances?

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
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