fcntl: support F_DUPFD_CLOEXEC on systems with fcntl Implement F_DUPFD_CLOEXEC. The unit test still fails on systems with other fcntl bugs (such as cygwin 1.5 mishandling F_DUPFD, or mingw lacking fcntl altogether). Passes on Linux, both with and without kernel support, and on cygwin 1.7. * modules/fcntl (Files): List new files. (configure.ac): Run a test. * m4/fcntl.m4 (gl_FUNC_FCNTL): New file. * lib/fcntl.c (rpl_fcntl): Likewise. * m4/fcntl_h.m4 (gl_FCNTL_H_DEFAULTS): Add witness defaults. (gl_FCNTL_H): Always replace fcntl.h. * modules/fcntl-h (Makefile.am): Substitute witnesses. * lib/fcntl.in.h (fcntl): Declare replacement. (F_DUPFD_CLOEXEC, GNULIB_defined_F_DUPFD_CLOEXEC): New macro when needed, plus a witness. * doc/posix-functions/fcntl.texi (fcntl): Document this. * doc/posix-headers/fcntl.texi (fcntl.h): Likewise. * tests/test-fcntl.c: New file. * modules/fcntl-tests: Likewise. Signed-off-by: Eric Blake <ebb9@byu.net>

# tmpdir.m4 serial 3
dnl Copyright (C) 2001-2002, 2006, 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.

# Prerequisites for lib/tmpdir.c

AC_DEFUN([gt_TMPDIR],
[
  AC_CHECK_FUNCS([__secure_getenv])
])