A prototype like functioname() only means that you are not making the argument types known at that point. Any call of the function that doesn’t match the implementation is an error though potentially hard to detect – so avoid this style of prototype. Rather explicitly use (void).

참고로 C++에서만 동치임. 이래소 틀딱들이 해주랬다 이소리한건데 혼자풀발기;; ㅋㅋㅋ