Warning: module holds reference to undefined symbol

[kylelanman]

One problem we faced a couple times this year was not providing an implementation of pure virtual functions in our subsystems and commands.

The two that come to mind are if your using a PIDSubsystem you have to implement.

virtual double ReturnPIDInput();
virtual void UsePIDOutput(double output);

In normal commands we implemented each command in it's own .h file.

We found our selves constantly leaving out implementations of empty methods.

ex.

~ArmUpCommand();
instead of
~ArmUpCommand() {}

and

Execute();
instead of
Execute() {}

The best way to narrow it down it down that we found is to comment all the subsystems and uncomment them one at a time until you can narrow it down to a particular subsystem or command.

If you'er still stumped then you can post that command or subsystem and the CD community can hopefully help you out.