Help: undefined reference to virtual table?

[Re, Vincent]

We're running G++ version 2.95.2 on Linux for S/390 and are having an error we 
don't understand. In our source code, we have: 

 ASMS_ESCON_Tape_Device::ASMS_ESCON_Tape_Device(const ASMS_ESCON_Tape_Device& 
dev)

This compiles fine, but when we link the code, we get:
 
 undefined reference to `ASMS_ESCON_Tape_Device::_ASMS_ESCON_Tape_Device 
virtual table'

Can someone explain this error to us? 

Thanks!

Vince Re 
Computer Associates