Re: [jamboost] propagation of usage-requirements

From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2004-12-16 06:13:38

Vladimir Prus wrote:

> 
> This is by design. In general, we don't know if 'libfoo' public headers 
> include headers from some_external_lib. If they do, we need to propagate 
> usage requirements. If they don't, we don't need.
> 

But this is exactly what usage requirements are about: they are 
requirements that are propagated, right ? So IIUC they are currently 
only propagated to their _direct_ dependents ?

> You can achieve the desired effect by:
> 
> lib libfoo : foo.cpp foo_dependencies : : : <use>foo_dependencies ;
> 

But if I now also have :

lib libbar : bar.cpp libfoo ;
exe app : app.cpp libbar ;

the usage-requirements are only propagated until libbar but not until 
'app'. Thus the include-path when compiling bar will not be influenced 
by the usage-requirements of foo_dependencies ?

> OTOH, I can't see any case where propagating usage requirements all the way up 
> will hurt, so maybe it's time to revise the behaviour. Opinions?

I definitly think it would be better to not only propagate 
usage-requirements to the direct dependents but also to the indirect 
dependents (i.e. dependents of dependents and so forth).

toon