Help interpreting load time error

[jhersh]

Originally Posted by mikets

I am expecting to see compiler errors if I made mistakes. But the compiler didn't complain and instead I got load time error of undefined symbol. Can somebody tell me what it means? Thanks.

The reason the compiler (it's actually the linker that would complain) is not giving you an error is that VxWorks links at load time instead of requiring a stub library for external linkage. Any symbols that are not defined when building are simply assumed to exist in the environment that you program will load in. If that does not hold true, you get errors from the loader.

[mikets]

I see. That makes sense now. So according to the linker error, am I missing the constructor of TrcRobot then?

[jhersh]

No... it's not the constructor. It's the vtable and the typeinfo.

If you run the tool C:\WindRiver\gnu\3.4.4-vxworks-6.3\x86-win32\bin\c++filtppc.exe and pass in the mangled name, it will tell you what it is in plain text.

[mikets]

Yes, you are right, it is the typeinfo and vtable. But what does it mean if these symbols are missing? TrcRobot is the base class of MyRobot. Why would the vtable of the TrcRobot be missing?

[jhersh]

Originally Posted by mikets

Yes, you are right, it is the typeinfo and vtable. But what does it mean if these symbols are missing? TrcRobot is the base class of MyRobot. Why would the vtable of the TrcRobot be missing?

You have not included the actual code, so it's a little hard to say, but I would speculate that you don't have a virtual destructor defined for TrcRobot. Since the RobotBase and SimpleRobot destructors are virtual and TrcRobot inherits from them and is then inherited from by MyRobot, you must have a virtual destructor at all levels of the hierarchy. Leaving it out of one class in the middle won't work. The default destructor is not virtual.

-Joe

[mikets]

Yes, I found it out yesterday. I thought I had an empty destructor defined but I missed that one. Thanks for the help.