On Wed, 2020-11-18 at 16:38 +0100, Tommaso Fonda wrote: > When using make 4.3, as packaged in OpenSUSE Tumbleweed and Ubuntu > 20.10, running "make" always rebuilds the whole kernel tree, even > when no files have changed since the last time I completed a build. > As soon as I roll back to make 4.2, the behaviour goes back to > normal. Is this a bug?
Well, since it's not the behavior you want there's clearly a bug SOMEWHERE. If what you mean is it a bug in GNU make, there's no way we can know that based on the info provided. It could also be a bug in your makefiles, that just happened to work OK for older versions of GNU make. Unfortunately I don't have the resources to check out your source tree and try to reproduce it, so someone else will have to do some investigation to narrow down the problem. The best way to do that is first, reduce the problem as much as possible; for example see if you can pass arguments to make so that it builds just one object file (the equivalent of "make foo.o" for example), where when you run that make command it doesn't rebuild with 4.2 but always rebuilds with 4.3. Then, run that command adding the --trace option to make and it should show you information on why it decided to rebuild. You can compare that between the 4.2 and 4.3 releases, and if it's not clear what the problem is please feel free to ask here again.
