The argument "0" is not automatically converted to the right type unless there is a prototype in scope. It isn't as important in this case because it is highly likely that the appropriate prototype has been #included, but it is a bigger deal if we're dealing with arguments for a variadic function. Anyway, it's good to be reminded what the declared types are.
Are you serious? Of course the question comes with the reasonable assumption that the proper declaration has been made especially since it’s a well known standard function. Additionally memset() is not a variadic function.
You said the types were corrected, you didn’t say you were reminding about the declaration types. The types were correct from the start.