In reply to rag123:
Did you check the compilation order, compiling the driver code before the code of the env?
There are a few weaknesses in your code:
(1) You are using a configuration object (my_config). You are constructing this, but you never assign a member to this.
(2) You are passing the virtuaöl interface to the config_db. But you never retrieve this from the config_db.
(3) It seems you are mixing your config object with the configuration db.