But you can also try to use IDE-agnostic solution like running the code through
unifdef and working with the result. If you just need to read the code, it's almost perfect solution. If you need to make some changes, things become a bit more complicated, but you can use git then to manage changes, like:
Of course, whether this approach will work or not depends on particular code base and what you're going to do with it, but it can be useful in some scenarios.