Re: [jamboost] Project requirements too global

From: Andrey Melnikov (melnikov_at_[hidden])
Date: 2005-08-12 13:43:12

Vladimir Prus wrote:
> Hi,
> I've a use case which is not very well supported by V2 at the moment:
> 
> project
> : requirements <library>/some_library_that_takes_long_time_to_build ;
> 
> lib runtime1 : main1.cpp common ;
> lib runtime2 : main2.cpp common ;
> lib common : common.cpp : <link>static ;
> 
> So, I have some library "common" that I made static to avoid the trouble of 
> installing yet another library. However, that library gets project 
> requirements too, and so tries to build 
> some_library_that_takes_long_time_to_build with <link>static. Now, I don't 
> want that at all, not to mention that static library can't be linked with 
> another static library.

Do you mean that you want to combine static common.lib with dynamic 
/some_library_that_takes_long_time_to_build ?

> However, there's no easy way to avoid this behaviour. I was thinking about 
> this:
> 
> lib common : common.cpp : local:<link>static ; 
> 
> to make requirement non-propagated, or about

I think a better idea is to make <link> always non-propagated. What are 
the use cases for which you'd like <link> to propagate?

> lib common : common.cpp : <no-project-requirements> ;
> 
> to avoid inheriting project requirements or about
> 
> lib common : common.cpp 
> : -<library>/some_library_that_takes_long_time_to_build
> ;
> 
> to selectively disable some of the project requirements.

This is too complicated. I think it would be better to split a project 
into several subprojects to selectively disable the requirements.

For small projects this can be complicated, so I'd like an ability to 
have multiple projects in a jamfile.

> The latter two can be useful for another use case:
> 
> project : requirements <library>util ;
> exe a1 .....
> exe a2 .....
> lib util : util.cpp ;
> 
> Now, this does not work, because util tries to build itself recursively.
> 

It would be better to write something like this:

project ;
exe a1 ..... util ... ;
exe a2 ..... util ... ;
lib util : util.cpp ;

If you have 100 executables (which is typical if you have each test 
isolated in its own binary) it's not a good idea to specify util 
dependency 100 times.

So in this case create a separate project for util:

project : <requirement>util-proj/util ;
exe a1 ..... ;
exe a2 ..... ;

project util-proj ;
lib util : util.cpp ;

Andrey