I was given a version of Arduino IDE v0016. It appears to be useful because code changed (e.g. Wire.cpp) will be automatically recompiled if the .o is deleted. But I do not find this convenience in the latest IDE v0021.
Am I missing something ? Wish someone can point me to a suitable document so that I can understand more about this in Development.
(probably, the Question can be rephrased as ... how to force library.cpp to recompile and be linked in v0021 ?)