AVR: Faster Interrupts, no size change.

Fixes arduino#2408

Author: xxxajk

hardware/arduino/avr/cores/arduino/WInterrupts.c

@@ -32,7 +32,37 @@
 
 #include "wiring_private.h"
 
-static volatile voidFuncPtr intFunc[EXTERNAL_NUM_INTERRUPTS];
+static void nothing(void) {
+}
+
+static volatile voidFuncPtr intFunc[EXTERNAL_NUM_INTERRUPTS] = {
+#if EXTERNAL_NUM_INTERRUPTS > 8
+    #warning There are more than 8 external interrupts. Some callbacks may not be initialized.
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 7
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 6
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 5
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 4
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 3
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 2
+    nothing,
+#endif
+#if EXTERNAL_NUM_INTERRUPTS > 1
+    nothing,
+#endif
+    nothing
+};
 // volatile static voidFuncPtr twiIntFunc;
 
 void attachInterrupt(uint8_t interruptNum, void (*userFunc)(void), int mode) {
@@ -238,7 +268,7 @@ void detachInterrupt(uint8_t interruptNum) {
 #endif
     }
 
-    intFunc[interruptNum] = 0;
+    intFunc[interruptNum] = nothing;
   }
 }
 
@@ -250,87 +280,71 @@ void attachInterruptTwi(void (*userFunc)(void) ) {
 
 #if defined(__AVR_ATmega32U4__)
 ISR(INT0_vect) {
-	if(intFunc[EXTERNAL_INT_0])
-		intFunc[EXTERNAL_INT_0]();
+    intFunc[EXTERNAL_INT_0]();
 }
 
 ISR(INT1_vect) {
-	if(intFunc[EXTERNAL_INT_1])
-		intFunc[EXTERNAL_INT_1]();
+    intFunc[EXTERNAL_INT_1]();
 }
 
 ISR(INT2_vect) {
-    if(intFunc[EXTERNAL_INT_2])
-		intFunc[EXTERNAL_INT_2]();
+    intFunc[EXTERNAL_INT_2]();
 }
 
 ISR(INT3_vect) {
-    if(intFunc[EXTERNAL_INT_3])
-		intFunc[EXTERNAL_INT_3]();
+    intFunc[EXTERNAL_INT_3]();
 }
 
 ISR(INT6_vect) {
-    if(intFunc[EXTERNAL_INT_4])
-		intFunc[EXTERNAL_INT_4]();
+    intFunc[EXTERNAL_INT_4]();
 }
 
 #elif defined(EICRA) && defined(EICRB)
 
 ISR(INT0_vect) {
-  if(intFunc[EXTERNAL_INT_2])
     intFunc[EXTERNAL_INT_2]();
 }
 
 ISR(INT1_vect) {
-  if(intFunc[EXTERNAL_INT_3])
     intFunc[EXTERNAL_INT_3]();
 }
 
 ISR(INT2_vect) {
-  if(intFunc[EXTERNAL_INT_4])
     intFunc[EXTERNAL_INT_4]();
 }
 
 ISR(INT3_vect) {
-  if(intFunc[EXTERNAL_INT_5])
     intFunc[EXTERNAL_INT_5]();
 }
 
 ISR(INT4_vect) {
-  if(intFunc[EXTERNAL_INT_0])
     intFunc[EXTERNAL_INT_0]();
 }
 
 ISR(INT5_vect) {
-  if(intFunc[EXTERNAL_INT_1])
     intFunc[EXTERNAL_INT_1]();
 }
 
 ISR(INT6_vect) {
-  if(intFunc[EXTERNAL_INT_6])
     intFunc[EXTERNAL_INT_6]();
 }
 
 ISR(INT7_vect) {
-  if(intFunc[EXTERNAL_INT_7])
     intFunc[EXTERNAL_INT_7]();
 }
 
 #else
 
 ISR(INT0_vect) {
-  if(intFunc[EXTERNAL_INT_0])
     intFunc[EXTERNAL_INT_0]();
 }
 
 ISR(INT1_vect) {
-  if(intFunc[EXTERNAL_INT_1])
     intFunc[EXTERNAL_INT_1]();
 }
 
 #if defined(EICRA) && defined(ISC20)
 ISR(INT2_vect) {
-  if(intFunc[EXTERNAL_INT_2])
     intFunc[EXTERNAL_INT_2]();
 }
 #endif