vm/state.go
func (st *State) Warnf(format string, args ...interface{}) {
	st.warn.Write([]byte(fmt.Sprintf(format, args...)))
}
func (st *State) Warnf(format string, args ...interface{}) {
	st.warn.Write([]byte(fmt.Sprintf(format, args...)))
}
// Warnf is used to generate warnings during virtual machine execution