How come I can't re-acquire the controlling terminal here

Code:

---

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>

void reterm(void)
{
  pid_t pid;
  if((pid = fork()) < 0) {
    fprintf(stderr, "can't fork\n");
    exit(1);
  }

  if(pid !=0)
    exit(1);

  if(setsid() < 0) {
    fprintf(stderr, "setsid error\n");
  }

}

int main(void)
{
  int fd;

  reterm();

  if((fd = open("/dev/null", O_RDONLY | O_NOCTTY)) < 0) {
    fprintf(stderr, "can't open tty\n");
    exit(1);
  }

  sleep(5000);
  close(fd);

  return 0;
}

---

[cd@localhost oakland]$ gcc -Wall reterm.c -o reterm
[cd@localhost oakland]$ ./reterm
[cd@localhost oakland]$ ps waux | grep reterm
cd 25021 0.0 0.0 1484 156 ? Ss 17:36 0:00 ./
reterm
cd 25031 0.0 0.1 3880 676 pts/3 R+ 17:36 0:00 grep
reterm
[cd@localhost oakland]$

Since when was /dev/null a tty?

Well, if I change it to /dev/tty like in the following

Code:

---

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <errno.h>

void reterm(void)
{
  pid_t pid;

  if((pid = fork()) < 0) {
    fprintf(stderr, "can't fork\n");
    exit(1);
  }

  if(pid !=0)
    exit(1);

  if(setsid() < 0)
    fprintf(stderr, "setsid error\n");
}

int main(void)
{

  int fd;

  reterm();

  if((fd = open("/dev/tty", O_RDONLY | O_NOCTTY)) < 0) {
    perror("Can't open /dev/tty: ");
    exit(1);
  }

  sleep(5000);
  close(fd);

  return 0;
}

---

I get

$ gcc -Wall reterm.c -o reterm
$ ./reterm
Can't open /dev/tty: : No such device or address
$ ls -al /dev/tty
crw-rw-rw- 1 root tty 5, 0 Aug 9 08:35 /dev/tty