[humanrebar]

On the other hand, the preprocessor is so dumb that having a normal variable or enum named "OK" or "STATUS" is a risk, even if all of your dependencies are clean. All it takes is a user to include your header and some header that #defines any name in your header to be something else.

So that means you really need to name your preprocessor symbols (and any other all-caps names, because that's the convention) in ways that probably won't collide. Like MYLIB_OK.

So it starts off dumb, but then you have to start layering on convention and defensive programming immediately. And it complicates entire other features of the language, naming constants and enumerated values especially.