Pages getting (deleted) when using shmget and shmat

I wrote the following 2 test programs, one that uses shmat and another that uses shmget and execve's the first binary.

The code is as follows :-

int main(int argc, char **argv) {
  void *retval;
  long shmid = atol(argv[1]);

  retval = shmat(shmid, NULL, SHM_RDONLY);
  printf("%p\n", retval);
}

And the wrapper file,

int setupshm(char *name) {
  int shmid;
  shmid = shmget(IPC_PRIVATE, 100, IPC_CREAT|0666);
  return shmid;
}

int main() {

  int pid = fork();
  if (pid == 0) {
  char **envp = NULL;
  char *argv[3];
  char num[10];

  sprintf(num, "%d", setupshm("whatever"));

  argv[1] = "./test";
  argv[2] = num;
  argv[3] = NULL;

  execve("./test", argv, envp);
}

else { int status; wait(pid, &status, 0); }
}

I run the wrapper program in gdb, intercept the execve, debug the test program, see that shmget succeeds; then inspect its /proc/pid/maps and I see that the page corresponding to the shmget shows up as "(Deleted)". Why does this happen? What am I doing wrong?