Re: [jamboost] Propagated features

From: David Abrahams (dave_at_[hidden])
Date: 2003-03-05 08:59:53

Vladimir Prus <ghost_at_[hidden]> writes:

> David Abrahams wrote:
>
>> > 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'.
>>
>> That doesn't make any sense. "No value" should only be possible for
>> optional features; since it's not optional, "console" is the default
>> and should be used.
>
> Your reasoning is sound. This does not work this way yet. The only way
> where default properties are applied is during expansion of build request,
> which happend on the top-level. So, non-propagated properties are stipped
> along the way, like I described.
>
> I've being thinking for some time about a change to overall build process. I 
> think that build request as given by user should be expanded, but default
> properties should not be added. After that, resulting property sets are
> passed to all directly requested main targets. Defaults will be added by
> main targets. 

That sounds perfectly correct.

"propagated" may be right for this feature, regardless. However, I
really don't understand what the MSVC option does at a deep level, so
it's hard to say for sure.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com