[Boost-build] Programmatically setting multiple requirements

Subject: [Boost-build] Programmatically setting multiple requirements
From: Anthony Foglia (AFoglia_at_[hidden])
Date: 2010-05-18 18:57:16

I have another question about creating static libraries linking to 
dynamically to system-wide libraries.  In this case, we have three 
variants, in two of which, we want to link to third-party libraries 
dynamically, and in the third, we want to link statically.

Because of the problem Gevorg Voskanyan outlined in this post 
<http://old.nabble.com/Handling-of-conflict-between-target's-requirements-and-its-dependencies'-usage-requirements-td28567264.html>, 
these need to be set up in the rules for each library that refers to the 
system file.

The rule for the system-wide library is in a file called sysdef.jam, 
defined as such:

lib rogue-wave-math                      #FOR: RW Math library
    : rogue-wave-linear-alg
      rogue-wave-lapack
    : <name>mth69 <search>$(rogue-wave-base)/lib
       <dll-path>$(rogue-wave-base)/lib
       <tag>@tag_rw
    :
    : <include>$(rogue-wave-base)
    ;

(And similar rules for rogue-wave-linear-alg and rogue-wave-lapack.)

Our current rule for the library:

lib Math
    : [ glob  src/*.cpp ]
      /sysdefs//rogue-wave-math
    : <include>./include
      <link>static
    :
    : <include>./include
    ;

which links (only statically).

The obvious solution is to make the /sysdefs//rogue-wave-math dependency 
conditional like so:

lib ASAMath
    : [ glob  src/*.cpp ]
    : <include>./include
      <link>static
      <variant>debug:<library>/sysdefs//rogue-wave-math/<link>shared
      <variant>release:<library>/sysdefs//rogue-wave-math/<link>shared
      <variant>production:<library>/sysdefs//rogue-wave-math/<link>static
    :
    : <include>./include
    ;

This works, but we use these libraries in more than one place, and the 
simpler I can make this more likely other people will follow this 
convention.  So I thought I could make a rule :

rule variant-link-rule ( library )
{
    local result = "" ;
    result += <variant>debug:<library>$(library)/<link>shared ;
    result += <variant>release:<library>$(library)/<link>shared ;
    result += <variant>production:<library>$(library)/<link>static ;
    ECHO "Variant link rule: $(library) -->" ;
    ECHO $(result) ;
    return "" $(result) ;
}

lib ASAMath
    : [ glob  src/*.cpp ]
    : <include>./include
      <link>static
       [ variant-link-rule /sysdefs//rogue-wave-math ]
    :
    : <include>./include
    ;

This is fails with the error:

$ bjam release -a -d+2
Variant link rule: /sysdefs//rogue-wave-math -->
  <variant>debug:<library>/sysdefs//rogue-wave-math/<link>shared 
<variant>release:<library>/sysdefs//rogue-wave-math/<link>shared 
<variant>production:<library>/sysdefs//rogue-wave-math/<link>static
/usr/share/boost-build/build/property.jam:320: in property.make from 
module property
error: '' is not a valid for property specification
/usr/share/boost-build/build/property-set.jam:390: in 
property-set.create-from-user-input from module property-set
/usr/share/boost-build/build/property-set.jam:446: in 
property-set.refine-from-user-input from module property-set
/usr/share/boost-build/build/targets.jam:1477: in 
targets.main-target-requirements from module targets
/usr/share/boost-build/tools/builtin.jam:532: in lib from module builtin
../../../lib/math/Jamfile:41: in modules.load from module 
Jamfile</home/AFoglia/projects/asa/trunk/lib/math>
/usr/share/boost-build/build/project.jam:312: in load-jamfile from 
module project
/usr/share/boost-build/build/project.jam:68: in project.load from module 
project
/usr/share/boost-build/build/project.jam:718: in project.use from module 
project
/usr/share/boost-build/build/project.jam:94: in load-used-projects from 
module project
/usr/share/boost-build/build/project.jam:79: in load from module project
/usr/share/boost-build/build/project.jam:120: in load-parent from module 
project
/usr/share/boost-build/build/project.jam:447: in initialize from module 
project
/usr/share/boost-build/build/project.jam:301: in load-jamfile from 
module project
/usr/share/boost-build/build/project.jam:68: in load from module project
/usr/share/boost-build/build/project.jam:170: in project.find from 
module project
/usr/share/boost-build/build-system.jam:248: in load from module 
build-system
/usr/share/boost-build/kernel/modules.jam:261: in import from module modules
/usr/share/boost-build/kernel/bootstrap.jam:132: in boost-build from module
/home/AFoglia/projects/asa/trunk/boost-build.jam:7: in module scope from 
module

What am I doing wrong?  Or is what I'm trying not possible?

-- 
Anthony Foglia
Princeton Consultants
[phone] x233