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+/* Duplicate an open file descriptor to a specified file descriptor.
+
+ Copyright (C) 1999, 2004-2007, 2009-2011 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* written by Paul Eggert */
+
+#include <config.h>
+
+/* Specification. */
+#include <unistd.h>
+
+#include <errno.h>
+#include <fcntl.h>
+
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+/* Get declarations of the Win32 API functions. */
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+#endif
+
+#if HAVE_DUP2
+
+# undef dup2
+
+int
+rpl_dup2 (int fd, int desired_fd)
+{
+ int result;
+# if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+ /* If fd is closed, mingw hangs on dup2 (fd, fd). If fd is open,
+ dup2 (fd, fd) returns 0, but all further attempts to use fd in
+ future dup2 calls will hang. */
+ if (fd == desired_fd)
+ {
+ if ((HANDLE) _get_osfhandle (fd) == INVALID_HANDLE_VALUE)
+ {
+ errno = EBADF;
+ return -1;
+ }
+ return fd;
+ }
+ /* Wine 1.0.1 return 0 when desired_fd is negative but not -1:
+ http://bugs.winehq.org/show_bug.cgi?id=21289 */
+ if (desired_fd < 0)
+ {
+ errno = EBADF;
+ return -1;
+ }
+# elif !defined __linux__
+ /* On Haiku, dup2 (fd, fd) mistakenly clears FD_CLOEXEC. */
+ if (fd == desired_fd)
+ return fcntl (fd, F_GETFL) == -1 ? -1 : fd;
+# endif
+ result = dup2 (fd, desired_fd);
+# ifdef __linux__
+ /* Correct a Linux return value.
+ <http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.30.y.git;a=commitdiff;h=2b79bc4f7ebbd5af3c8b867968f9f15602d5f802>
+ */
+ if (fd == desired_fd && result == (unsigned int) -EBADF)
+ {
+ errno = EBADF;
+ result = -1;
+ }
+# endif
+ if (result == 0)
+ result = desired_fd;
+ /* Correct a cygwin 1.5.x errno value. */
+ else if (result == -1 && errno == EMFILE)
+ errno = EBADF;
+# if REPLACE_FCHDIR
+ if (fd != desired_fd && result != -1)
+ result = _gl_register_dup (fd, result);
+# endif
+ return result;
+}
+
+#else /* !HAVE_DUP2 */
+
+/* On older platforms, dup2 did not exist. */
+
+# ifndef F_DUPFD
+static int
+dupfd (int fd, int desired_fd)
+{
+ int duplicated_fd = dup (fd);
+ if (duplicated_fd < 0 || duplicated_fd == desired_fd)
+ return duplicated_fd;
+ else
+ {
+ int r = dupfd (fd, desired_fd);
+ int e = errno;
+ close (duplicated_fd);
+ errno = e;
+ return r;
+ }
+}
+# endif
+
+int
+dup2 (int fd, int desired_fd)
+{
+ int result = fcntl (fd, F_GETFL) < 0 ? -1 : fd;
+ if (result == -1 || fd == desired_fd)
+ return result;
+ close (desired_fd);
+# ifdef F_DUPFD
+ result = fcntl (fd, F_DUPFD, desired_fd);
+# if REPLACE_FCHDIR
+ if (0 <= result)
+ result = _gl_register_dup (fd, result);
+# endif
+# else
+ result = dupfd (fd, desired_fd);
+# endif
+ if (result == -1 && (errno == EMFILE || errno == EINVAL))
+ errno = EBADF;
+ return result;
+}
+#endif /* !HAVE_DUP2 */