1 files changed, 50 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/unlockpt.c b/sysdeps/unix/sysv/linux/unlockpt.c
new file mode 100644
index 0000000000..e508b280c5
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/unlockpt.c
@@ -0,0 +1,50 @@
+/* Copyright (C) 1998 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <errno.h>
+#include <stdlib.h>
+
+/* Given a fd on a master pseudoterminal, clear a kernel lock so that
+   the slave can be opened.  This is to avoid a race between opening the
+   master and calling grantpt() to take possession of the slave.  */
+int
+unlockpt (fd)
+     int fd __attribute__ ((unused));
+{
+#ifdef TIOCSPTLCK
+  int serrno = errno;
+  int unlock = 0;
+
+  if (ioctl (fd, TIOCSPTLCK, &unlock))
+    {
+      if(errno == EINVAL)
+	{
+	  __set_errno (serrno);
+	  return 0;
+	}
+      else
+	return -1;
+    }
+#else
+  /* On pre-/dev/ptmx kernels this function should be a no-op.  */
+  return 0;
+#endif
+}