When you compile a model with external functions Vensim will automatically embed a function stub in the mdl.c file for callbacks to Vensim that access the external function. You should not need to make any changes to Vensim's compiled simulation files.
Previous versions of Vensim required that external function bodies in additional .obj files be linked for compiled simulations. This can still be done by defining LINKEXTERN in vensim.h but this is not recommended.
