Re: [Boost-build] Best way to include platform specific sources?

From: Vladimir Prus (ghost_at_[hidden])
Date: 2006-02-10 03:46:08

Hi Daniel,

> I was looking at this piece of Jamfile again:

> alias linux ;
> obj linux
>
>     : # sources
>
>         linux.cpp
>
>     : # requirements
>
>         <os>LINUX
>     ;
.......

> ========== Example 2 ==========
> rule platform-specific-source ( )
> {
>     import os ;
>     local files ;
>     switch [ os.name ]
>     {
>         case NT : ;
>         case LINUX :
>             files += linux.cpp
>             ;
>         case OSXPPC :
>             files += osxppc.cpp
>             ;
>     }
>     return $(files) ;
> }
>
> exe example2 : [ platform-specific-source ] ;

That's just fine, if the build platform and the target platforms is the same 
-- which is the case now since we don't, at least officially, support 
cross-compiling.

> and it almost works, but since we don't have any NT specific files, the
> rule bombs out.

Ah, true, but what do you want in that case? Skip building of 'example2' 
completely? Then, you can either wrap it in "if [ os.name ] = NT", or you can 
use newly introduced <build>no properties:

   exe example2 : [ platform-specific-source ] : <os>NT:<build>no ;

or you can combine indirect conditional requirements with <build>on and the 
<source> feature like this:

        rule sources ( properties * )
        {
              if <variant>debug in $(properties)
               {
                        return <source>a_d.cpp ;
         }
                 else if <variant>release in $(properties)
         {
                     return <source>a_r.cpp ;
               }
              else
               {
                     return <build>no ;
              }
        }
        
        exe main : : <conditional>@sources ;

I've used <varint> for testing, you'll use <os> feature. Here's what I get:

    ghost_at_zigzag$ bjam debug
    [...]
    gcc.compile.c++ bin/gcc/debug/a_d.o
    [...]
    ghost_at_zigzags$ bjam release
    [...]
    gcc.compile.c++ bin/gcc/release/a_r.o
    [...]
    ghost_at_zigzag:/space/p2/ghost/build/boost.build/sources$ bjam profile
    Skipping build of ./main -- <build>no in properties.

HTH,
Volodya