Question

#include <iostream>
#include <stdlib.h>

int main(int argc, char *argv[])
{

  int num=-2147483648;
  int positivenum=-num;
  int absval=abs(num);

  std::cout<<positivenum<<"\n";
  std::cout<<absval<<"\n";

  return 0;
}

Hi I am quite curious why the output of the above code is

-2147483648
-2147483648

Now I know that -2147483648 is the smallest represntable number among signed ints, (assuming an int is 32 bits). I would have assumed that one would get garbage answers only after we went below this number. But in this case, [phone] IS covered by the 32 bit system of integers. So why the negative answer in both cases?

Answer 1

But in this case, [phone] IS covered by the 32 bit system of integers.

Not quite correct. It only goes up to [phone]. So your assumption isn’t right.

Negating -2147483648 will indeed produce 2147483648, but it will overflow back to -2147483648.

Furthermore, signed integer overflow is technically undefined behavior.