another frustrating dead end in C where I need fancier language features

state_machine.c

struct state {
  int some_info;
  void (*next)(struct state *s);
};
void end(struct state *s) {
  // do some clean up
  s->some_info = 0;
  s->next = halt;
}
void bar(struct state *s) {
  s->some_info = 987;
  s->next = end;
}
void branch( struct state *s) {
  if( s->some_info == 100) {
    // this is the branch
    s->next = go_to_address(addr); // this is illegal. you can't compose functions like this
  }
}
void go_to_address(struct state *s, int addr ) {
  if( outsidePMemory(addr) ) {
    s->next = exception;
  }
  s->next = get_instr_at(addr);
}
void foo(struct state *s) {
  if( s->some_info < 0) {
    // something no-no-bad-computer happened
    s->next = exception;
    return;
  }
  // do whatever you're gonna do
  s->some_info *= 321;
  s->next = NULL; // get next
}
void run() {
  struct state s = { 123, foo};
  while( s.next != halt) {
    s.next = s.next == NULL ? get_next_instr() : s.next;
    (*s.next)(&s);
  }
}