That will only work for open source libraries. It won't work for libraries provided in binary form (which is common in commercial contexts I've worked in so far

That will only work for open source libraries. It won't work for libraries provided in binary form (which is common in commercial contexts I've worked in so far). I also tend to dislike the preprocessor and other forms of syntactic programming in favour of solutions working on the semantic level. The more I know about the preprocessor, the less simple and more puzzling it is to me, especially after implementing it.