Add an unpatched version of xz, XZ Utils, to /trunk/deps/third_party

xz/src/common/tuklib_open_stdxxx.c

+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       tuklib_open_stdxxx.c
+/// \brief      Make sure that file descriptors 0, 1, and 2 are open
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "tuklib_open_stdxxx.h"
+
+#ifndef TUKLIB_DOSLIKE
+#       include <stdlib.h>
+#       include <errno.h>
+#       include <fcntl.h>
+#       include <unistd.h>
+#endif
+
+
+extern void
+tuklib_open_stdxxx(int err_status)
+{
+#ifdef TUKLIB_DOSLIKE
+        // Do nothing, just silence warnings.
+        (void)err_status;
+
+#else
+        for (int i = 0; i <= 2; ++i) {
+                // We use fcntl() to check if the file descriptor is open.
+                if (fcntl(i, F_GETFD) == -1 && errno == EBADF) {
+                        // With stdin, we could use /dev/full so that
+                        // writing to stdin would fail. However, /dev/full
+                        // is Linux specific, and if the program tries to
+                        // write to stdin, there's already a problem anyway.
+                        const int fd = open("/dev/null", O_NOCTTY
+                                        | (i == 0 ? O_WRONLY : O_RDONLY));
+
+                        if (fd != i) {
+                                // Something went wrong. Exit with the
+                                // exit status we were given. Don't try
+                                // to print an error message, since stderr
+                                // may very well be non-existent. This
+                                // error should be extremely rare.
+                                (void)close(fd);
+                                exit(err_status);
+                        }
+                }
+        }
+#endif
+
+        return;
+}