[Boost-build] How to build project comprising of sources in different dirs

From: Frank Birbacher (bloodymir.crap_at_[hidden])
Date: 2008-05-06 08:33:56

Hi!

 From the beginning of using BJam I repeatedly run into the following 
problem:

I have several projects where sources are distributed in different 
directories. These projects usually build a client and a serer 
executable as well as a client shared library. These targets share 
common code. I put this code into a single directory and the other 
sources are split up into "server", "client", and "lib" directories.

How am I supposed to build the "common" code in a way that
  (1) compiles the code only once for each build variant
  (2) works regardless of link=shared or static
  (3) works with gcc and msvc alike

My first guess was:

# in /common dir:
lib common : [ glob *.cpp ] /boost//filesystem ... ;

# in /server dir:
exe server : [ glob *.cpp ] ../common//common ;

This satisfies (1), but (2) only when using gcc, because for DLLs I 
would have to litter the code with __declspec(dllim-/export) which I 
don't want to. If I only do a static build then the boost libs will be 
linked statically, too, which I don't want to. Mixing dyn boost libs 
with a static common lib opens another can of worms.

Second guess:

alias common : [ glob *.cpp ] /boost//filesystem ... ;

This satisfies (2) and (3), but for each use the code is compiled again, 
increasing compile times significantly: the "server", the "client", and 
the "lib" each compile the code again.

Current guess:

To solve this I tried the following:

rule bundle ( name : sources + : others * : ureq * )
{
        local objs ;
        for s in $(sources) {
                objs += [ obj $(s:S=) : $(s) $(others) ] ;
        }
        alias $(name) : $(objs) : : : $(ureq) ;
}

bundle common :
                [ glob *.cpp ]
        :
                /boost//filesystem
                /boost//system
        :
                <include>.
        ;

This way (1), (2), and (3) are satisfied, at least with msvc and cygwin.

And I wonder if anyone has had the same problem and I wonder why there 
is no such rule in BJam already (maybe with a different name). Could 
such a rule become part of bjam? Or is there another way to solve this?

Regards, Frank