C++ code - 6 lines

Link:

C++, pasted on Feb 18:

int main()
{
  int n = 1;
  int a[n];
  return 0;
}

Output:

1
2
3

In function 'int main()':
Line 4: error: ISO C++ forbids variable-size array 'a'
compilation terminated due to -Wfatal-errors.