Re: [Boost-build] Conditional targets not resolving properly

Subject: Re: [Boost-build] Conditional targets not resolving properly
From: Matthew Chambers (matthew.chambers_at_[hidden])
Date: 2009-09-10 11:05:01

Indirect conditionals are my preferred solution for this case.

rule exclude-source-if-not-gcc ( properties * )
{
   if ! <toolset>gcc in $(properties) { return <source>SOURCE.cpp ; }
}

project A
  : requirements
    <link>static
    <toolset>gcc:<cxxflags>-DNO_SMART
  : usage-requirements
    <linkflags>-lA
    <include>.
  ;

alias commonsources
  :  (snip)
  ;

lib libA
  : commonsources
  : <conditional>@exclude-source-if-not-gcc
  ;

HTH,
-Matt

Johan Larsson wrote:
> Hello.
>
> As part of a project, I have a library with an associated Jamfile I 
> need to build. I want to build this particular library as a static 
> lib, so I've added <link>static to the project requirements in the 
> Jamfile for the library. So far so good.
>
> However, I also want to exclude a particular source file from the 
> library if I use a particular toolset (gcc in this case). So I've 
> created two targets; one with all the sources and no particular 
> requirements, and one without the source file in question with 
> <toolset>gcc added as a requirement, like so:
>
>
>
> project A
>   : requirements
>     <link>static
>     <toolset>gcc:<cxxflags>-DNO_SMART
>   : usage-requirements
>     <linkflags>-lA
>     <include>.
>   ;
>
> alias commonsources
>   :  (snip)
>   ;
>
> lib libA
>   : commonsources
>     SOURCE.cpp
>   ;
>
> lib libA
>   : commonsources
>   : <toolset>gcc
>   ;
>
> The problem is that when building with a toolset that is not gcc, bjam 
> fails to find an appropriate target. The output it gives me is as follows:
> error: No best alternative for ./libA
>     next alternative: required properties: <link>static
>         not matched
>     next alternative: required properties: <link>static <toolset>gcc
>         not matched
>
> Obviously, I want the builds to match the closest possible 
> alternative; that is, any build with a toolset other than gcc should 
> match the first target, and any build with gcc as a toolset should 
> match the second target.
>
> Is there a way to achieve this, or perhaps a different way altoghether 
> to exclude source files from a target when build with a particular 
> toolset?
> ------------------------------------------------------------------------
>
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