Arduino Mega2560 reboots after two consecutive calls to analogWrite

Question

Why does this code lead to Arduino Mega2560 constantly resetting?

void setup() {
  Serial.begin(9600);
  Serial.println("SETUP");
  delay(500);             //without this line Serial prints "SESESESESE"
  analogWrite(10, 100);
  analogWrite(11, 50);    //reboots after this line
}

void loop() {
  Serial.println("LOOP"); //doesn't reach here
}

Arduino serial outputs the following:

SETUP
SETUP
SETUP
SETUP
SETUP
SETUP
SETUP
SETUP

Things to note:

1) Arduino does not reboot if I substitute pins 10 and 11 with some others (8 and 9 for example), but it does also reboot with pins 12 and 13 (I guess pins 10-13 are somehow special).

2) Arduino does not reboot if I use equal values in the calls to analogWrite (100 and 100 for example).

Answer 1

This behavior should not happen, if you set your pins to:

 void setup() {
    pinMode(10, OUTPUT);  // sets the pin as output
    pinMode(11, OUTPUT);  // sets the pin as output

Such resets are typical of a bad power supply, noise or bad connections, (bad protoboard), or a bad LED pin (eg; resistor too small or damaged, or damaged pin, etc). If your mega has no HW-defect and a sufficient power source or additional HW attached that causes this defect, it should work as expected.

Answer 2

Apparently, the compiler's optimizations are to blame. After adding these two lines at the start of the program it finally works as it should:

void setup() __attribute__((optimize("-O1")));
void loop() __attribute__((optimize("-O1")));