--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2009-08-23  Bruno Haible  <bruno@clisp.org>
+
+	New module 'accept4'.
+	* lib/sys_socket.in.h (accept4): New declaration.
+	* lib/accept4.c: New file.
+	* m4/accept4.m4: New file.
+	* m4/sys_socket_h.m4 (gl_SYS_SOCKET_H_DEFAULTS): Initialize
+	GNULIB_ACCEPT4, HAVE_ACCEPT4.
+	* modules/sys_socket (Makefile.am): Substitute GNULIB_ACCEPT4,
+	HAVE_ACCEPT4.
+	* modules/accept4: New file.
+	* doc/glibc-functions/accept4.texi: Mention the new module.
+
 2009-08-24  Jim Meyering  <meyering@redhat.com>
 
 	progname: also set global program_invocation_name, when possible

--- a/doc/glibc-functions/accept4.texi
+++ b/doc/glibc-functions/accept4.texi
@@ -2,15 +2,15 @@
 @subsection @code{accept4}
 @findex accept4
 
-Gnulib module: ---
+Gnulib module: accept4
 
 Portability problems fixed by Gnulib:
 @itemize
-@end itemize
-
-Portability problems not fixed by Gnulib:
-@itemize
 @item
 This function is missing on all non-glibc platforms:
 MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin, mingw, Interix 3.5, BeOS.
 @end itemize
+
+Portability problems not fixed by Gnulib:
+@itemize
+@end itemize

new file mode 100644
--- /dev/null
+++ b/lib/accept4.c
@@ -0,0 +1,108 @@
+/* Accept a connection on a socket, with specific opening flags.
+   Copyright (C) 2009 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <sys/socket.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include "binary-io.h"
+
+#ifndef SOCK_CLOEXEC
+# define SOCK_CLOEXEC 0
+#endif
+
+int
+accept4 (int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags)
+{
+  int fd;
+
+  /* Check the supported flags.  */
+  if ((flags & ~(SOCK_CLOEXEC | O_TEXT | O_BINARY)) != 0)
+    {
+      errno = EINVAL;
+      return -1;
+    }
+
+  fd = accept (sockfd, addr, addrlen);
+  if (fd < 0)
+    return -1;
+
+#if SOCK_CLOEXEC
+# if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+/* Native Woe32 API.  */
+  if (flags & SOCK_CLOEXEC)
+    {
+      HANDLE curr_process = GetCurrentProcess ();
+      HANDLE old_handle = (HANDLE) _get_osfhandle (fd);
+      HANDLE new_handle;
+      int nfd;
+
+      if (!DuplicateHandle (curr_process,	    /* SourceProcessHandle */
+			    old_handle,		    /* SourceHandle */
+			    curr_process,	    /* TargetProcessHandle */
+			    (PHANDLE) &new_handle,  /* TargetHandle */
+			    (DWORD) 0,		    /* DesiredAccess */
+			    FALSE,		    /* InheritHandle */
+			    DUPLICATE_SAME_ACCESS)) /* Options */
+	{
+	  close (fd);
+	  errno = EBADF; /* arbitrary */
+	  return -1;
+	}
+
+      /* Closing fd before allocating the new fd ensures that the new fd will
+	 have the minimum possible value.  */
+      close (fd);
+      nfd = _open_osfhandle ((long) new_handle,
+			     O_NOINHERIT | (flags & (O_TEXT | O_BINARY)));
+      if (nfd < 0)
+	{
+	  CloseHandle (new_handle);
+	  return -1;
+	}
+      return nfd;
+    }
+# else
+/* Unix API.  */
+  if (flags & SOCK_CLOEXEC)
+    {
+      int fcntl_flags;
+
+      if ((fcntl_flags = fcntl (fd, F_GETFD, 0)) < 0
+	  || fcntl (fd, F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
+	{
+	  int saved_errno = errno;
+	  close (fd);
+	  errno = saved_errno;
+	  return -1;
+	}
+    }
+# endif
+#endif
+
+#if O_BINARY
+  if (flags & O_BINARY)
+    setmode (fd, O_BINARY);
+  else if (flags & O_TEXT)
+    setmode (fd, O_TEXT);
+#endif
+
+  return fd;
+}

--- a/lib/sys_socket.in.h
+++ b/lib/sys_socket.in.h
@@ -423,5 +423,31 @@
 
 #endif /* HAVE_SYS_SOCKET_H */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if @GNULIB_ACCEPT4@
+# if !@HAVE_ACCEPT4@
+/* Accept a connection on a socket, with specific opening flags.
+   The flags are a bitmask, possibly including O_CLOEXEC (defined in <fcntl.h>)
+   and O_TEXT, O_BINARY (defined in "binary-io.h").
+   See also the Linux man page at
+   <http://www.kernel.org/doc/man-pages/online/pages/man2/accept4.2.html>.  */
+extern int accept4 (int sockfd, struct sockaddr *addr, socklen_t *addrlen,
+		    int flags);
+# endif
+#elif defined GNULIB_POSIXCHECK
+# undef accept4
+# define accept4(s,a,l,f) \
+    (GL_LINK_WARNING ("accept4 is unportable - " \
+                      "use gnulib module accept4 for portability"), \
+     accept4 (s, a, l, f))
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _GL_SYS_SOCKET_H */
 #endif /* _GL_SYS_SOCKET_H */

new file mode 100644
--- /dev/null
+++ b/m4/accept4.m4
@@ -0,0 +1,19 @@
+# accept4.m4 serial 1
+dnl Copyright (C) 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,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_ACCEPT4],
+[
+  AC_REQUIRE([gl_SYS_SOCKET_H_DEFAULTS])
+
+  dnl Persuade glibc <sys/socket.h> to declare accept4().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_FUNCS_ONCE([accept4])
+  if test $ac_cv_func_accept4 != yes; then
+    HAVE_ACCEPT4=0
+    AC_LIBOBJ([accept4])
+  fi
+])

--- a/m4/sys_socket_h.m4
+++ b/m4/sys_socket_h.m4
@@ -1,4 +1,4 @@
-# sys_socket_h.m4 serial 12
+# sys_socket_h.m4 serial 13
 dnl Copyright (C) 2005-2009 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -140,6 +140,8 @@
   GNULIB_SENDTO=0;      AC_SUBST([GNULIB_SENDTO])
   GNULIB_SETSOCKOPT=0;  AC_SUBST([GNULIB_SETSOCKOPT])
   GNULIB_SHUTDOWN=0;    AC_SUBST([GNULIB_SHUTDOWN])
+  GNULIB_ACCEPT4=0;     AC_SUBST([GNULIB_ACCEPT4])
   HAVE_STRUCT_SOCKADDR_STORAGE=1; AC_SUBST([HAVE_STRUCT_SOCKADDR_STORAGE])
   HAVE_SA_FAMILY_T=1;   AC_SUBST([HAVE_SA_FAMILY_T])
+  HAVE_ACCEPT4=1;       AC_SUBST([HAVE_ACCEPT4])
 ])

new file mode 100644
--- /dev/null
+++ b/modules/accept4
@@ -0,0 +1,28 @@
+Description:
+accept4() function: accept a connection on a socket, with specific opening
+flags.
+
+Files:
+lib/accept4.c
+m4/accept4.m4
+
+Depends-on:
+sys_socket
+accept
+fcntl
+binary-io
+
+configure.ac:
+gl_FUNC_ACCEPT4
+gl_SYS_SOCKET_MODULE_INDICATOR([accept4])
+
+Makefile.am:
+
+Include:
+<sys/socket.h>
+
+License:
+LGPL
+
+Maintainer:
+Bruno Haible, Simon Josefsson

--- a/modules/sys_socket
+++ b/modules/sys_socket
@@ -44,10 +44,12 @@
 	      -e 's|@''GNULIB_SENDTO''@|$(GNULIB_SENDTO)|g' \
 	      -e 's|@''GNULIB_SETSOCKOPT''@|$(GNULIB_SETSOCKOPT)|g' \
 	      -e 's|@''GNULIB_SHUTDOWN''@|$(GNULIB_SHUTDOWN)|g' \
+	      -e 's|@''GNULIB_ACCEPT4''@|$(GNULIB_ACCEPT4)|g' \
 	      -e 's|@''HAVE_WINSOCK2_H''@|$(HAVE_WINSOCK2_H)|g' \
 	      -e 's|@''HAVE_WS2TCPIP_H''@|$(HAVE_WS2TCPIP_H)|g' \
 	      -e 's|@''HAVE_STRUCT_SOCKADDR_STORAGE''@|$(HAVE_STRUCT_SOCKADDR_STORAGE)|g' \
 	      -e 's|@''HAVE_SA_FAMILY_T''@|$(HAVE_SA_FAMILY_T)|g' \
+	      -e 's|@''HAVE_ACCEPT4''@|$(HAVE_ACCEPT4)|g' \
 	      -e '/definition of GL_LINK_WARNING/r $(LINK_WARNING_H)' \
 	      < $(srcdir)/sys_socket.in.h; \
 	} > $@-t && \