Yep. If it was opt-in in a per-makefile way, it would be ok (or preferably opt-out). I think cmake got this absolutely right, fwiw. You define the version of c

Yep. If it was opt-in in a per-makefile way, it would be ok (or preferably opt-out). I think cmake got this absolutely right, fwiw. You define the version of cmake you're writing against, and they go to great pains to ensure that they preserve behaviour even in newer versions of cmake. As an example, we could have a special variable: make_ver = 4.5 And even running with a future version of make the behaviour would be that of 4.5. if it's not present, it defaults to the latest version before the versions were introduced. This would let make do things like accept spaces instead of tabs, be parallel by default, etc in future versions while presenting old behaviour.