[OE-core] DEPENDS tranlation with BBCLASSEXTEND

[Khem Raj]

On Mon, Mar 28, 2011 at 12:03 PM, Tom Rini <tom_rini at mentor.com> wrote:
> On 03/27/2011 04:03 PM, Chris Larson wrote:
>> On Sun, Mar 27, 2011 at 1:08 PM, Khem Raj <raj.khem at gmail.com> wrote:
>>> I observed that if I have
>>> DEPENDS = "a b" in recipe.bb which has BBCLASSEXTEND = "native"
>>> then dependecies for recipe-native shows a-native b-native so far so
>>> good
>>>
>>> Now if I want to add a dependency which only is needed for native recipe
>>> I do
>>>
>>> DEPENDS_virtclass-native += "c-native"
>>>
>>> what this does is it will ignore a-native and b-native dependencies and
>>> only adds "c-native" to depends of native recipe
>>>
>>> DEPENDS_virtclass-native_append = " c-native"
>>>
>>> This does what I wanted i.e. have deps on a-native b-native c-native
>>>
>>> I think behavior of += or _append should be similar. Is my understanding
>>> correct ?
>>
>> They've never been the same.  += is immediate, _append is delayed.  If
>> a class, say, native.bbclass, defines the variable with ?=, and you
>> used += before the inherit, then it will have a value, and the ?=
>> won't assign.  I assume native.bbclass does it this way today so you
>> can override the automatic behavior by defining the variable yourself,
>> but I'll let Richard speak to that decision.
>
> As Richard said, this is a good summary.  And a shorter still summary
> (as Chris reminds me everytime I forget) is that since BBCLASSEXTENDS
> makes use of an override already (virtclass-native/cross/etc) you must
> keep that in mind when further modifying it as you get not what you
> expected but what you asked for.
>

Yes no doubt on how it works and can be coded to likings of what we
have but I think
that having += and friends as well as _append and _prepend could be
combined into one logic
immediate appending/prepending operation may be confusing IMO while
immediate assignments
I think still are ok. We have more than one directives doing very
similar yet semantically different operations
It becomes hard for recipe writers. May be I am over simplifying

> --
> Tom Rini
> Mentor Graphics Corporation
>
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