6.5.2.2 Function calls p6 より > 6 If the expression that denotes the called function has a type that does not include a > prototype, ... (snip) > If the number of arguments does not equal the number of parameters, the > behavior is undefined. If the function is defined with a type that includes a prototype, and > either the prototype ends with an ellipsis (, ...) or the types of the arguments after > promotion are not compatible with the types of the parameters, the behavior is undefined.
