I've seen this sort of thing all the time. Not the part about different preprocessor defines in different files, but about having a struct's contents depend on

I've seen this sort of thing all the time. Not the part about different preprocessor defines in different files, but about having a struct's contents depend on some compile time conditions. It comes up when you want to track extra debug information but only for debug builds. It comes up if you need to store platform specific information in a common struct. It can come up if you have a major feature that you want to toggle on/off at compile time. Etc.