Defensive Programming Squad

In this thread we pick up innocent programs and tank the shit out of them.

#include <stdio.h>
int main () {
  int n1, n2;
  printf("First integer:");
  scanf("%d", &n1);
  printf("Second integer:");
  scanf("%d", &n2);
  printf("Sum = %d\n", n1+n2);
  return 0;
}

>>1
The main declaration is invalid C99 code.
The printf statements might display after scanf has taken input due to line buffering.
And of course there is the complete lack of error checking.