[oe] RFC: thinking about DEPENDS properties

[Koen Kooi]

On 27-01-09 12:07, Robert Schuster wrote:
> Hi,
> today I was thinking about some missing semantics in OE's DEPENDS
> variable and had the idea of reusing the way we write SRC_URI entries
> for them.
>
> The issues:
>
> 1) Strong dependencies
>
> Some recipes have a strong dependency on another recipe. Take llvm as an
> example. llvm puts a bunch of static libraries (.a) and object code
> files into staging which another program links to. So, if llvm is
> recompiled (e.g. changed CFLAGS or applied a patch) those having a
> dependency on llvm should be recompiled as well.

Isn't that what BB_STAMP_POLICY=whitelist and BB_STAMP_POLICY=full 
accomplish?

regards,

Koen


>
> In order to express this, I would write:
>
> DEPENDS += "llvm;strong=true"
>
> 2) Minimum&  Maximum supported versions
> Some recipes cannot be built with certain versions of other recipes.
>
> DEPENDS += "automake-native;minver=1.10"
>
> If the distro uses a lower automake version OE should error out when
> someone tries to build that recipe:
>
> ERROR: Recipe 'foo' needs at least 'automake-native 1.10' but
> 'PREFERRED_VERSION_automake-native' is set to '1.9.6'.
>
> --
>
> I know this brings in a lot of complicated things to think about, e.g.
> what is the result of:
>
> foo.inc: DEPENDS = "bar;minver=0.8;maxver=0.9"
>
> foo_1.0: require foo.inc
>           DEPENDS += "bar;minver=1.0"
>
> Perhaps to many components in OE already expect DEPENDS to be a
> whitespace separated list of words and we should be add another variable
> whose only purpose is to set properties for existing DEPENDS entries:
>
>
> foo_1.0:
>   require foo.inc
>   # Replaces value from foo.inc
>   DEPENDSPROPS = "bar;minver=1.0"
>
> --
>
> My main concern is that the knowledge about which recipe can live in
> harmony with another is currently implicit. There is no way to express
> this except by writing a comment (which is almost never done).
>
> Regards
> Robert
>
>
>
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