Re: [boost] [preprocessor] computed include possible?

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2006-04-08 15:50:10

Roland Schwarz wrote:
> I am wondering if it would be possible to write a computed include macro 
> that is sufficiently compiler independent?
> 
> E.e. given a macro
> 
> #define BOOST_PLATFORM_INCLUDE(hdr) ... definition missing ...
> 
> which should be usable as:
> 
> #include BOOST_PLATFORM(foo.h)
> 
> The effect being win32/foo.h included on one linux/foo.h included on 
> another platform.
> 
> I have yet figured out a way that can achieve something close, but gcc 
> does not allow to use a parameterized macro.

Where is the problem?

    #if defined(linux) || defined(__linux) || defined(__linux__)
    #  define PLATFORM_HEADER_DIRECTORY linux
    #elif defined(_WIN32) || defined(__WIN32__) || defined(WIN32)
    #  define PLATFORM_HEADER_DIRECTORY windows
    // [...]
    #endif

    #define PLATFORM_HEADER(header) <PLATFORM_HEADER_DIRECTORY/header>

    #include PLATFORM_HEADER(foo.h)

Should work. I've no idea how portable it is, though. 

If you need quotes instead use BOOST_PP_STRINGIZE:

    #define PLATFORM_HEADER(header) \
        BOOST_PP_STRINGIZE(PLATFORM_HEADER_DIRECTORY/header)

Regards,

Tobias