[PATCH] dup2: work around Haiku bug

[Eric Blake]

dup2(n,n) must be a no-op, but on Haiku, it resets FD_CLOEXEC.
However, we must keep the Linux workaround for dup2(n,n)
returning (unsigned int)-EBADF.

* m4/dup2.m4 (gl_FUNC_DUP2): Test for bug.
* lib/dup2.c (rpl_dup2) [!WIN32]: Add workaround.
* doc/posix-functions/dup2.texi (dup2): Document the bug.
* tests/test-dup2.c (main): Enhance test.

Signed-off-by: Eric Blake <address@hidden>
---

This fixes './gnulib-tool --with-tests --test dup2 cloexec' on Haiku.

 ChangeLog                     |    8 ++++++++
 doc/posix-functions/dup2.texi |    5 +++++
 lib/dup2.c                    |    4 ++++
 m4/dup2.m4                    |   23 +++++++++++++++++------
 tests/test-dup2.c             |    5 +++++
 5 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 360f0dd..b025454 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2011-01-31  Eric Blake  <address@hidden>
+
+       dup2: work around Haiku bug
+       * m4/dup2.m4 (gl_FUNC_DUP2): Test for bug.
+       * lib/dup2.c (rpl_dup2) [!WIN32]: Add workaround.
+       * doc/posix-functions/dup2.texi (dup2): Document the bug.
+       * tests/test-dup2.c (main): Enhance test.
+
 2011-01-31  Simon Josefsson  <address@hidden>

        doc: off_t is not available in eglibc 2.11.2 stdio.h.
diff --git a/doc/posix-functions/dup2.texi b/doc/posix-functions/dup2.texi
index 59bad08..fc1e359 100644
--- a/doc/posix-functions/dup2.texi
+++ b/doc/posix-functions/dup2.texi
@@ -17,6 +17,11 @@ dup2
 mingw.

 @item
+This function resets the @code{FD_CLOEXEC} flag when duplicating an fd
+to itself on some platforms:
+Haiku.
+
address@hidden
 This function returns 0 for @code{dup2 (1, 1)} on some platforms:
 Cygwin 1.5.x.

diff --git a/lib/dup2.c b/lib/dup2.c
index 6b72f7b..e00dc7b 100644
--- a/lib/dup2.c
+++ b/lib/dup2.c
@@ -59,6 +59,10 @@ rpl_dup2 (int fd, int desired_fd)
       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__
diff --git a/m4/dup2.m4 b/m4/dup2.m4
index bc2f417..def263b 100644
--- a/m4/dup2.m4
+++ b/m4/dup2.m4
@@ -1,4 +1,4 @@
-#serial 11
+#serial 12
 dnl Copyright (C) 2002, 2005, 2007, 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -8,7 +8,7 @@ AC_DEFUN([gl_FUNC_DUP2],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([AC_CANONICAL_HOST])
-  AC_CHECK_FUNCS_ONCE([dup2])
+  AC_CHECK_FUNCS_ONCE([dup2 fcntl])
   if test $ac_cv_func_dup2 = no; then
     HAVE_DUP2=0
     AC_LIBOBJ([dup2])
@@ -16,16 +16,25 @@ AC_DEFUN([gl_FUNC_DUP2],
     AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
       [AC_RUN_IFELSE([
          AC_LANG_PROGRAM([[#include <unistd.h>
+#include <fcntl.h>
 #include <errno.h>]],
            [int result = 0;
-            if (dup2 (1, 1) == 0)
+#if HAVE_FCNTL
+            if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
               result |= 1;
+#endif HAVE_FCNTL
+            if (dup2 (1, 1) == 0)
+              result |= 2;
+#if HAVE_FCNTL
+            if (fcntl (1, F_GETFD) != FD_CLOEXEC)
+              result |= 4;
+#endif
             close (0);
             if (dup2 (0, 0) != -1)
-              result |= 2;
+              result |= 8;
             /* Many gnulib modules require POSIX conformance of EBADF.  */
-            if (dup2 (1, 1000000) == -1 && errno != EBADF)
-              result |= 4;
+            if (dup2 (2, 1000000) == -1 && errno != EBADF)
+              result |= 16;
             return result;
            ])
         ],
@@ -40,6 +49,8 @@ AC_DEFUN([gl_FUNC_DUP2],
              gl_cv_func_dup2_works=no;;
            freebsd*) # on FreeBSD 6.1, dup2(1,1000000) gives EMFILE, not EBADF.
              gl_cv_func_dup2_works=no;;
+           haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
+             gl_cv_func_dup2_works=no;;
            *) gl_cv_func_dup2_works=yes;;
          esac])
       ])
diff --git a/tests/test-dup2.c b/tests/test-dup2.c
index 35aa6ca..e2ad88b 100644
--- a/tests/test-dup2.c
+++ b/tests/test-dup2.c
@@ -169,7 +169,12 @@ main (void)
   ASSERT (dup2 (fd + 1, fd + 1) == fd + 1);
   ASSERT (!is_inheritable (fd + 1));
   ASSERT (dup2 (fd + 1, fd + 2) == fd + 2);
+  ASSERT (!is_inheritable (fd + 1));
   ASSERT (is_inheritable (fd + 2));
+  errno = 0;
+  ASSERT (dup2 (fd + 1, -1) == -1);
+  ASSERT (errno == EBADF);
+  ASSERT (!is_inheritable (fd + 1));
 #endif

   /* On systems that distinguish between text and binary mode, dup2
-- 
1.7.3.5