The key part in the bindings, for this matter, is what the function's return value is. It indicates the number of Lua return values, so one would expect a zero (since the C++ function returns zero values). Unfortunately ToLua generates an output for any reference, even const refs, so you'll see `return 1` in the bindings code. All the `tolua_pushXXX` right before the return is the return values being pushed onto the stack, so you can deduce their types from that.