Could s/body give me a hint about why the segmentation fault happens in my case?

__harry

Hi dudes,
It's just a piece of code from a textbook, which tries to finish a zombie process by capturing SIGCHLD signal. However, when the child process terminates, I got a segmentation fault.
I have no idea of the root cause. Could anybody give me a little hint? /THK
My environment is Debian 7.4.0/gcc 4.7.2

void clean_up_child(int sig_num) {
  int status;
  wait(&status);
}

int main(int argc, char* argv[]) {
  char *arglist[] = {
    "ls",
    "-l",
    "/",
    NULL
  };
  struct sigaction sigchld_action;
  memset(&sigchld_action, 0, sizeof(sigaction));
  sigchld_action.sa_handler = clean_up_child;
  sigaction(SIGCHLD, &sigchld_action, NULL);

  pid_t child_pid = fork();
  if (0 != child_pid) {
  }
  else {
    execvp("ls", arglist);
  }

  for (;{}
  return 0;
}

harry@debian:~/sandbox/foo$ ./foo
total 84
drwxr-xr-x   2 root root  4096 Feb 20 10:15 bin
drwxr-xr-x   3 root root  4096 Feb 20 10:20 boot
......
lrwxrwxrwx   1 root root    24 Feb 20 09:37 vmlinuz -> boot/vmlinuz-3.2.0-4-486
Segmentation fault