[piaste]

It was a theoretical question. It's not the first time I hear the complaint '$previous_dev left a bunch of unmaintainable macro tricks in a C codebase' and I thought, since those macros get expanded as part of the compilation process, surely it should be possible to intercept and capture the expanded version?

Even if a whitelist is not available (the SO question involves a particular C++ preprocessor and may not apply to others), a hacky approach might be to comment out all the #defines in the codebase, uncomment the ones you want to get rid of, and then run the full preprocessor task on it. Ugly but probably doable for a one-time refactoring.