Not exactly. As of C17, the function definition you wrote implies that the function has no arguments, just like in C++. However, a declaration that is not part

Not exactly. As of C17, the function definition you wrote implies that the function has no arguments, just like in C++. However, a declaration that is not part of a definition, like void fun(); (which you typically find in a header file) indeed does not say anything about the function's arguments. You have to write void fun(void); to specify that the function takes no arguments. For consistency, you can (and probably should) also use that style in the function's definition, but you don't have to. Anyway, C23 will align C's behavior with C++: void fun() will mean the same thing as void fun(void), whether as part of a function definition or not.