Doubt about the Serial port Arduino

Official Hardware Mega Due
8 
void serialEventRun(void) {

  if (Serial.available()) interrupcion_serie0();
  if (Serial1.available()) interrupcion_serie1();

}

//FUNCION ATENCIÓN INTERRUPCIÓN PUERTO SERIE0//

void interrupcion_serie0() {
  while (Serial.available()) {
    char inChar_0 = (char)Serial.read();
    inputString_0 += inChar_0;
    if ((inChar_0 == '\r') || (inputString_0.length() == buffer_0)) {
      stringComplete_0 = true;
    }
  }
}

//FUNCION ATENCIÓN INTERRUPCIÓN PUERTO SERIE1//

void interrupcion_serie1() {
  while (Serial1.available()) {
    char inChar_1 = (char)Serial1.read();
    inputString_1 += inChar_1;
    if ((inChar_1 == '\r') || (inputString_1.length() == buffer_1)) {
      stringComplete_1 = true;
    }
  }
}

This will never be triggered on a serialEvent trigger, unless you have a magic library, that you did not declared, running in background.

This:

extern void serialEventRun(void) __attribute__((weak));

Really exist, but it has no point if it's to call an event in the same program file. The point of this, is to call a function in your program from a library, for example.