[Bug stdio/17909] New: getline/getdelim sets errno to ENOTTY after trying to read from /dev/null

["luther.ansynod at yopmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17909

            Bug ID: 17909
           Summary: getline/getdelim sets errno to ENOTTY after trying to
                    read from /dev/null
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: stdio
          Assignee: unassigned at sourceware dot org
          Reporter: luther.ansynod at yopmail dot com

On Linux, if I run the test program below with stdin redirected from
a normal empty file, I get the following output, as expected:

$ touch empty-file
$ ./getline-test < empty-file
rval: -1, feof: 1, ferror: 0, errno: 0 (Success)

However, if I try to read from /dev/null, I get the following:

$ ./getline-test < /dev/null
rval: -1, feof: 1, ferror: 0, errno: 25 (Inappropriate ioctl for device)

errno 25 is ENOTTY, which is not one of the error values that
getline/getdelim should return, according to POSIX
<http://pubs.opengroup.org/onlinepubs/9699919799/functions/getdelim.html>

I would expect errno to be 0 in this case, as no error occurred, from
the point of view of the caller of getline().

//----------------------------------------
// getline-test.c

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

int
main (int arg, char **argv)
{
  char *bufp = NULL;
  size_t bufsize = 0;
  ssize_t rval;
  int err;

  errno = 0;
  rval = getline (&bufp, &bufsize, stdin);
  err = errno;
  printf ("rval: %d, feof: %d, ferror: %d, errno: %d (%s)\n",
          rval, feof (stdin), ferror (stdin), err, strerror (err));
  free (bufp);
  return 0;
}

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