Is negating INT_MIN undefined behaviour?

Question

Let\'s say I have a variable i that comes from external sources:

int i = get_i();

Assuming i is INT_MIN

Answer 1

Is negating INT_MIN undefined behaviour?

Yes, when INT_MIN < -INT_MAX - which is very common (2's complement). It is integer overflow.

int i = get_i();

#if INT_MIN < -INT_MAX
if (i == INT_MIN) {
  fprintf(stderr, "Houston, we have a problem\n");
  // Maybe return or exit here.
}
#endif 

int j = -i;

Houston, we have a problem