error: ‘__s_getMD5Sum’ is not a member of ‘boost::shared_ptr＜const test::gps_＜std::allocator＜void＞

error: ‘_s_getMD5Sum’ is not a member of ‘boost::shared_ptr<const test::gps<std::allocator > >’ return M::__s_getMD5Sum().c_str();

解决：

把void gpsCallback( test::gps::ConstPtr &msg)改为void gpsCallback(const test::gps::ConstPtr &msg)