How Arduino IDE pre-processing work?

econjack:
PaulS: I thought OP understood that the IDE and compiler are separate entities. Rereading his post, perhaps not.

From the original post I got the impression that the OP understood the distinction correctly - the issue is the misguided and poorly implemented mucking about that the IDE does to your code before invoking the compiler, and nothing to do with the C++ compiler / preprocessor.