[Boost-build] Conditional, via macros, includes and dependency scanning.

From: Rene Rivera (grafikrobot_at_[hidden])
Date: 2007-10-01 11:28:52

Following up to the build list...

John Maddock wrote:
> Rene Rivera wrote:
>> Rene Rivera wrote:
>>> John Maddock wrote:
>>>> (bjam can't trace dependencies through the config headers).
>>> Really? Why not?
>> Never mind I see why it can't. You are using macros in the includes.
> 
> Right, and most of the time that's what we want: we don't a rebuild of 
> *everything* for compiler X, if the config for compiler Y has been patched.

Yea, I can see how that would be annoying. Well just in case you want to 
contemplate adding those dependencies in. You can do something like:

// GCC-XML emulates other compilers, it has to appear first here!
#   define BOOST_COMPILER_CONFIG "boost/config/compiler/gcc_xml.hpp"
#if 0 // for dependency analysis
#   include <boost/config/compiler/gcc_xml.hpp>
#endif

Or possibly:

// GCC-XML emulates other compilers, it has to appear first here!
#   define BOOST_COMPILER_CONFIG "boost/config/compiler/gcc_xml.hpp"
// For dependency analysis: #include <boost/config/compiler/gcc_xml.hpp>

And I guess we could also try to put something into Boost.Build for 
handling toolset conditional includes. Perhaps allowing to add something 
like:

// #depends <boost/config/compiler/comeau.hpp> <toolset>como

?

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