Abort instead of segfault with clear memory violation

Question

I came upon this weird behaviour when dealing with C strings. This is an exercise from the K&R book where I was supposed to write a function that appends one string onto

Answer 1

int main() {
  char s1[] = "hello";
  char s2[] = "eheheheheheh"; 
  printf("%s\n", strcat(s1, s2));
}

instead use:

   int main() {
  char s1[20] = "hello";
  char s2[] = "eheheheheheh"; 
  printf("%s\n", strcat(s1, s2));
}