I never had any false negatives, they are basically impossible in this framework, except it does assume if a program, and all it's inputs are unchanged, the output is unchanged, so this is no good for programs which randomly produce different outputs.
ccache can cause things to get built twice, because the first run it sees it tries to read a file, then later writes to it, so it knows something different might happen if you run again -- but then again that is just ccache doing it's thing, so it's quick. Yes, distcc wouldn't work, but then again I find distcc super-brittle (so hard to make sure everything has the same compiler versions, etc), I may have used it 20 years ago, but I don't think I ever would now!
ccache can cause things to get built twice, because the first run it sees it tries to read a file, then later writes to it, so it knows something different might happen if you run again -- but then again that is just ccache doing it's thing, so it's quick. Yes, distcc wouldn't work, but then again I find distcc super-brittle (so hard to make sure everything has the same compiler versions, etc), I may have used it 20 years ago, but I don't think I ever would now!