In Rules.make Makefiles, it's a common bug for someone to forget the 'X' for a file that exports symbols. I want to let every source file export symbols if it wants to, at low cost. Remember, we write a few common Makefiles, and dozens of kernel developers write the bulk of the Makefiles. It's hard to do syntax checking in a fluid language like Make, but we can detect some things. Correctness trumps efficiency.
Correctness comes first.
I have a vision of accomplishing things by exploiting list operations. At some point I want to get beneath the wish lists into our various architectural visions. We already have a nice mailing list that should be mentioned too. Separate kernel version. If a target need the version we simply add the dependency.