The calculation of md5 checksum of geometry_msgs/PoseWithCovariance seems wrong. It should be c23e848cf1b7533a8d7c259073a97e6f according to rosmsg md5 command, but gengo produces 620fbdfad1a8bc89c4d876fdb4ffa7f8 for this. The sums of all child nodes Point, Quaternion, Pose are correct.