+ return fd;
+}
+
+/* Returns a file descriptor equivalent to FD, except that the resulting file
+ descriptor is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
+ FD must be open and non-inheritable. The result will be non-inheritable as
+ well.
+ If FD < 0, FD itself is returned. */
+static int
+fd_safer_noinherit (int fd)
+{
+ if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
+ {
+ /* The recursion depth is at most 3. */
+ int nfd = fd_safer_noinherit (dup_noinherit (fd));
+ int saved_errno = errno;
+ close (fd);
+ errno = saved_errno;
+ return nfd;
+ }
+ return fd;
+}
+
+/* Duplicates a file handle, making the copy uninheritable and ensuring the
+ result is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
+ Returns -1 for a file handle that is equivalent to closed. */
+static int
+dup_safer_noinherit (int fd)
+{
+ return fd_safer_noinherit (dup_noinherit (fd));
+}
+
+/* Undoes the effect of TEMPFD = dup_safer_noinherit (ORIGFD); */
+static void
+undup_safer_noinherit (int tempfd, int origfd)
+{
+ if (tempfd >= 0)
+ {
+ if (dup2 (tempfd, origfd) < 0)
+ error (EXIT_FAILURE, errno, _("cannot restore fd %d: dup2 failed"),
+ origfd);
+ close (tempfd);
+ }
+ else
+ {
+ /* origfd was closed or open to no handle at all. Set it to a closed
+ state. This is (nearly) equivalent to the original state. */
+ close (origfd);
+ }