I was just curious about how the AVR architecture manages errors that would cause a regular desktop program to crash. I'm talking about logical errors for example math problems that are undefined. Such as division by 0 and getting a square root of a negative number. At first I was expecting that by giving an error to the AVR chip it will just return 0. But I ran this program:
void setup() {
Serial.begin(9600);
}
void loop(){
int x = 0;
int p = 50;
int result;
result = p/x;
Serial.println(result);
result = sqrt(-10);
delay(1000);
Serial.println(result);
delay(10000);
}
and got this output:
4294967295
0
After this I got really confused. Why would the result
variable take the maximum value of an unsigned long
? Since I declared an int
the micro controller must have dedicated 2 bytes of dynamic memory to this variable but apparently it somehow managed to get additional 2 bytes to store the data. Could this mean that the AVR chip can corrupt data in other memory locations while allocating new data for the variable that just was fed a undefined in to it? Okay maybe the AVR chip just sets any mathematical nonsense to 4294967295. But no in the example of getting the square root of -10 we see that the value became 0. Although this is probably a function processed by some library so maybe there is some kind of protection against these errors. Also, I tried to run the program above but with a byte
variable for the result
instead of int
.
void setup() {
Serial.begin(9600);
}
void loop(){
int x = 0;
int p = 50;
int result;
result = p/x;
Serial.println(result);
result = sqrt(-10);
delay(1000);
Serial.println(result);
delay(10000);
}
And the result was the same. So, is there some kind of documentation about error management in AVR since this is important to know while development.
P.S. Everything was run on a real Atmega 328p chip on an arduino nano.