Re: [UI] system libraries

From: Markus Schöpflin (markus.schoepflin_at_[hidden])
Date: 2002-11-26 09:03:56

Vladimir Prus wrote:

> I has thinking about the way system libraries are
> used. For now, there's inherited from V1 method
> 
> exe a : a.cpp : <find-library>zlib <library-file>helper.a ;
> 
> There are some problems:
> 
> 1. <find-library> is long and non-intuitive.
> 
> 2. It differs from using library targets, for no good
> reason. Moreover, consider that on Windows, a library
> called 'expat' must be built by Boost.Build, so we
> have to write
> 
> exe main : main.cpp : <library>expat
> 
> But on Linux this library is already awailable, so we better
> use
> 
> exe main : main.cpp : <find-library>expat
> 
> This difference is messy.

I don't follow you here. Why do have to build 'expat' with boost build 
on windows? Don't they have a Makefile for this that we better use?

> 
> 3. I remember that Markus requested that "find-library" had
> static and dynamic version (i.e "link this system library
> statically"). But
> 
> <find-library-static>zlib

That's what I currently have in my local version of V1.

> is just too long. An further, if 10 applications use zlib,
> do they all have to specify it?

I would say yes. They should specify it.

> So, I propose to
> 
> 1. Kick "find-library". Introduce new "system-lib" target type.
> For example:
> 
> system-lib zlib ;

Why would you need this declaration? To tag on build specifiactions?

> exe a : a.cpp : <library>zlib ;
> 
> It's possible to specify static linking
> 
> system-lib zlib : <shared>false ;

But this implies that all exe targets in a single Jamfile link to the 
zlib statically, doesn't it? Not so good, IMO.

Or would it be possible to say, for example:

system-lib zlib-dynamic : <shared>true <real-name>zlib ;
system-lib zlib-static : <shared>false <real-name> zlib ;

And later either

exe a : a.cpp : <library>zlib-dynamic ;

or

exe b : b.cpp : <library>zlib-static ;

> There will be some implementation gotchas, but they're
> not serious. How does it look from the interface standpoint?
> 
> 2. Kick <library-file> as well. Allow to specify file name as value
> of <library> features.
> 
> exe a : a.cpp : <library>zlib <library>helper.a ;

How do you distinguish between file names and library names? Via 
presence of system-lib declaration?

> For me, this looks like a pure enhancement.
> 
> - Volodya

Hmm, as long as you don't loose the flexibility to specify things 
individually for each target, I would agree.

Markus