The compiler-based dependecies have a problem that causes objects to be rebuilt when they are up to date. Here's what happens, 1. Build a fresh tree. 2. Build again without clobber. Everything gets rebuilt! 3. Build again without clobber, dependencies work properly. I know what's happening and I have a fix (in config/rules.mk). I will check it in when the tree opens, or sooner if the problem is considered serious enough.

I checked in a fix. If this does not work, I would suggest pulling the *.pp files out of the .deps directory. This is what the plain vanilla -MD flag does. It's simpler, but then you see all the extra files in your object directory.