source: CIVL/mods/dev.civl.com/examples/sideEffects/errSideEffectsInGuards.cvl@ cb4d4f4

$input int a[10];
$assume($forall (int i : 0 .. 9) a[i] == 0);
int proc(int i) {
  if (i == 0)
    $when(*(a+9) == 0) return 0;
  else
    $when(*(a+9) == 0 && *(a+10) == 0) return 1;  // guard with error side effect will evaluate to false

}

int main() {
  $parfor(int i : 0 .. 1)
    proc(i);
  return 0;
}