Vendors will implement full state machines in the preprocessor. Generated code will include the same header 2 or 3 times, because each time through, the state machine has changed and different code is exposed.
I am not joking.
My point isn't that the rules apply universally, it's that something found to be a good practice in a safety critical industry is flagrantly discarded in another, without good reason. Literal state machines in the preprocessor. Metaprogramming in C. But because it is generated code, it is "ok."
I should really find a different field, for my mental well being.