-fno-common makes sure we do not have multiple declarations of the same global symbol across compilation units. It helps debug nasty linkage bugs by guaranteeing that all reference to a global symbol use the same underlying object. It also helps avoiding benign mistakes such as declaring enum as global objects instead of types in headers (hence the minor fixes scattered across the source). Change-Id: I55c16406dc54ff8a6860238b90ca990fa6b179f1 Signed-off-by: Benoît Ganne <bganne@cisco.com>