Is this a problem? The very big problem with the preprocessor approach is, in my opinion, that it's awkward to add a new platform. With Robert's approach you just add some new files and don't touch the existing code. With the preprocessor approach you need write access to the source code of the library in question, I'd say.
Which do you add more often, a new platform or a new function? Robert's approach makes the first easy and the second hard; the preprocessor makes the second easy and (you claim) the first hard. The right choice is clear, then: if you add new functions to your API more often than new platforms, use the preprocessor; if you add new platforms more often than new functions, use Robert's approach. In any case, I think thatwith well-designed macros, preprocessing allows new platforms to be handled in a localised and easy way in most cases. --KW 8-)