Or, rather, pointers, in this case.
Anyway, the pointer to an object in this case is room *current_room, which is declared in the globalObs.h which I don't have uploaded. It's the only thing in globablObs.h, though, so yeah.
Basically, when compiling the .os', everything seems to work. On linking, though, I get an error which basically says that, in main_loop.cpp, I'm redifing current_room, which is first defined in classes.cpp. I'm guessing I'm either misusing pointers or preprocessor directives here.