From 21a0a9e3ef07b457b04d483f8dd216bbdf06e860 Mon Sep 17 00:00:00 2001
From: Eric Blake <ebb9@byu.net>
Date: Mon, 7 Dec 2009 21:08:17 -0700
Subject: [PATCH] dup2: fix logic bugs

If the platform has dup2, don't register with fchdir if the
destination was -1.

If the platform lacks dup2 (are there any these days?), then don't
close the destination unless the source is valid, make sure errno
is correct, and only register with fchdir on fcntl (since dup is
already overridden to do a registration).

* lib/dup2.c (dup2): Fix logic bugs.  Use HAVE_DUP2 rather than
REPLACE_DUP2 to decide when rpl_dup2 is needed.
* m4/dup2.m4 (gl_REPLACE_DUP2): Only define REPLACE_DUP2 when dup2
exists.
(gl_FUNC_DUP2): Drop unneeded AC_SUBST.

Signed-off-by: Eric Blake <ebb9@byu.net>
---
 ChangeLog  |  9 +++++++++
 lib/dup2.c | 30 ++++++++++++++++--------------
 m4/dup2.m4 |  8 ++++----
 3 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7b78dca31..40d2dacc8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2009-12-08  Eric Blake  <ebb9@byu.net>
+
+	dup2: fix logic bugs
+	* lib/dup2.c (dup2): Fix logic bugs.  Use HAVE_DUP2 rather than
+	REPLACE_DUP2 to decide when rpl_dup2 is needed.
+	* m4/dup2.m4 (gl_REPLACE_DUP2): Only define REPLACE_DUP2 when dup2
+	exists.
+	(gl_FUNC_DUP2): Drop unneeded AC_SUBST.
+
 2009-12-07  Eric Blake  <ebb9@byu.net>
 
 	unlink: fix m4 detection
diff --git a/lib/dup2.c b/lib/dup2.c
index 140af1b9f..7ce49a2b7 100644
--- a/lib/dup2.c
+++ b/lib/dup2.c
@@ -32,7 +32,7 @@
 # include <windows.h>
 #endif
 
-#if REPLACE_DUP2
+#if HAVE_DUP2
 
 # undef dup2
 
@@ -70,14 +70,14 @@ rpl_dup2 (int fd, int 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 == desired_fd)
-    result = _gl_register_dup (fd, desired_fd);
-#endif
+# if REPLACE_FCHDIR
+  if (fd != desired_fd && result != -1)
+    result = _gl_register_dup (fd, result);
+# endif
   return result;
 }
 
-#else /* !REPLACE_DUP2 */
+#else /* !HAVE_DUP2 */
 
 /* On older platforms, dup2 did not exist.  */
 
@@ -102,19 +102,21 @@ dupfd (int fd, int desired_fd)
 int
 dup2 (int fd, int desired_fd)
 {
-  int result;
-  if (fd == desired_fd)
-    return fcntl (fd, F_GETFL) < 0 ? -1 : 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 REPLACE_FCHDIR
-  if (0 <= result)
-    result = _gl_register_dup (fd, desired_fd);
-#endif
+  if (result == -1 && (errno == EMFILE || errno == EINVAL))
+    errno = EBADF;
   return result;
 }
-#endif /* !REPLACE_DUP2 */
+#endif /* !HAVE_DUP2 */
diff --git a/m4/dup2.m4 b/m4/dup2.m4
index a74e915bb..26a6f60e3 100644
--- a/m4/dup2.m4
+++ b/m4/dup2.m4
@@ -1,4 +1,4 @@
-#serial 9
+#serial 10
 dnl Copyright (C) 2002, 2005, 2007, 2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -46,13 +46,13 @@ AC_DEFUN([gl_FUNC_DUP2],
       gl_REPLACE_DUP2
     fi
   fi
-  AC_DEFINE_UNQUOTED([REPLACE_DUP2], [$REPLACE_DUP2],
-    [Define to 1 if dup2 returns 0 instead of the target fd.])
 ])
 
 AC_DEFUN([gl_REPLACE_DUP2],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
-  REPLACE_DUP2=1
+  if test $ac_cv_func_dup2 = yes; then
+    REPLACE_DUP2=1
+  fi
   AC_LIBOBJ([dup2])
 ])
-- 
2.11.0