Standard streams and vfork

I have been playing around with fork / vfork functions a bit and there is something that puzzles me. Stevens's book states that:

Note that in Figure 8.3 we are calling _exit instead of exiting.

As we described in section 7.3, _exit does not perform any flushing of the standard I / O buffers. If we call exit, the results are undefined. Depending on the implementation of the standard I / O library, we might not see a difference in the output, or we might find that the output from the parent printf is gone. If the child calls exit, the implementation flushes the standard I / O streams. If this is the only action taken by the library, then we will not see any difference with the result generated if the child called _exit. However, if the implementation also closes standard I / O streams, the memory representing the FILE object for standard output will be flushed. Since the child borrows the parent's address space when the parent resumes and calls printf,no output appears and printf will return -1. Note that the parent STDOUT_FILENO is still valid, as the child receives a copy of the parent file descriptor array (see Figure 8.2). Most modern exit implementations don't bother to close threads. As the process is about to terminate, the kernel will close all file descriptors open in the process. Closing them in a library just adds overhead without any benefit.discovered in this process. Closing them in a library just adds overhead without any benefit.discovered in this process. Closing them in a library just adds overhead without any benefit.

so i tried to check if i could get printf error, my vfork manual has:

All open streams of stdio (3) are flushed and closed. Files created by tmpfile (3) are removed.

but when I compile and execute this program:

  #include<stdio.h>
  #include<stdlib.h>
  #include<unistd.h>
  #include<sys/types.h>
  #include<sys/wait.h>

  int main()
{
  int s;
  pid_t ret;
  if (vfork() == 0)
  {
      //abort();
      exit(6);
  }
  else
  {
      ret=wait(&s);
      printf("termination status to %d\n",s);
      if (WIFEXITED(s))
          printf("normalnie, status to %d\n",WEXITSTATUS(s));
  }
  return 0;
}

      

        
        
        
      

    

everything works fine, i don't get any printf errors. Why is this?