Remove check for NULL buffer passed to `ptsname_r'

`ptsname_r' is declared in stdlib.h to only accept a `nonnull'
second argument and therefore GCC may choose to make optimizations
based on the assumption that this argument is NULL. This means
that potentially, GCC can optimize away the NULL check at some
point in the future. Since this is a programming interface, we
might as well remove the NULL check ourselves.

This also warrants a change to the `ptsname_r' manual page that
must be submitted to the corresponding mailing list.

In addition, remove the NULL buffer test in login/tst-ptsname.c.

3 files changed, 6 insertions, 7 deletions

diff --git a/ChangeLog b/ChangeLog
index f74004b39a..4c06d7ef85 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2017-06-07  Arjun Shankar  <arjun.is@lostca.se>
 
+	* sysdeps/unix/sysv/linux/ptsname.c (__ptsname_internal):
+	Remove check for NULL 'buf'.
+	* login/tst-ptsname.c (do_test): Remove test with NULL 'buf'.
+
+2017-06-07  Arjun Shankar  <arjun.is@lostca.se>
+
 	* sysdeps/unix/sysv/linux/tst-clone2.c: Do not
 	include test-skeleton.c.
 	Include support/check.h and support/test-driver.c.
diff --git a/login/tst-ptsname.c b/login/tst-ptsname.c
index be8744dfd0..96f0449788 100644
--- a/login/tst-ptsname.c
+++ b/login/tst-ptsname.c
@@ -70,7 +70,6 @@ do_test (void)
   if (fd != -1)
     {
       result |= do_single_test (fd, buf, sizeof (buf), 0);
-      result |= do_single_test (fd, NULL, sizeof (buf), EINVAL);
       result |= do_single_test (fd, buf, 1, ERANGE);
       close (fd);
     }
diff --git a/sysdeps/unix/sysv/linux/ptsname.c b/sysdeps/unix/sysv/linux/ptsname.c
index e3f2ae8ff2..41bb0bbb0e 100644
--- a/sysdeps/unix/sysv/linux/ptsname.c
+++ b/sysdeps/unix/sysv/linux/ptsname.c
@@ -72,12 +72,6 @@ __ptsname_internal (int fd, char *buf, size_t buflen, struct stat64 *stp)
   int save_errno = errno;
   unsigned int ptyno;
 
-  if (buf == NULL)
-    {
-      __set_errno (EINVAL);
-      return EINVAL;
-    }
-
   if (!__isatty (fd))
     {
       __set_errno (ENOTTY);