struct Point {
  int x;
  int y;
};

void init_point(struct Point *p);
struct Point new_point();

void f() {
  struct Point p1, p2;
  init_point(&p1);
  p2 = new_point(); // equivalent, potentially slower
}

void init_point(struct Point *p) {
  p->x = 0;
  (*p).y = 0;
}

struct Point* dangling_point() {
  struct Point ans;
  ans.x = 0;
  ans.y = 0;
  return &ans; // really bad idea!
}

struct Point new_point() {
  struct Point ans;
  ans.x = 0;
  ans.y = 0;
  return ans; // no problem
}

void wrong_update_x(struct Point p, int new_x) {
  // this function has no effect on anything
  p.x = new_x;
}

void update_x(struct Point * p, int new_x) {
  p->x = new_x;
}