Propagated features (Was: [Boost-build] CVS: boost/tools/build/new msvc.jam,1.10,1.11)

From: Vladimir Prus (ghost_at_[hidden])
Date: 2003-03-04 02:53:03

David Abrahams wrote:
> Update of /cvsroot/boost/boost/tools/build/new
> Log Message:
> Add user-interface feature; won't build .exes otherwise!
[..]
> +import feature : feature ;
> +
> +feature user-interface : console gui wince native auto ;

Dave, this has caused a problem. Consider

lib l : l.cpp ;
exe a : a.cpp l ;

Both targets are build with default value of 'user-interface': 'console', and
that's right. However, when building "a", you also have to build "l". Since
user-interface is not propagated, "l" is build for a second time, this time
without any value of 'user-interface'. 

I've made the feature propagated. Is this corresponds to the semantics?
In general, we probably should have a rule that all non-free non-incidental
features should be declared propagated. I don't mean to enforce this rule in
the code, but just a guideline for adding new features.

- Volodya