2 dnl Copyright (C) 2002, 2005, 2007, 2009-2015 Free Software Foundation,
4 dnl This file is free software; the Free Software Foundation
5 dnl gives unlimited permission to copy and/or distribute it,
6 dnl with or without modifications, as long as this notice is preserved.
8 AC_DEFUN([gl_FUNC_DUP2],
10 AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
11 AC_REQUIRE([AC_CANONICAL_HOST])
12 AC_CHECK_FUNCS_ONCE([getdtablesize])
13 m4_ifdef([gl_FUNC_DUP2_OBSOLETE], [
14 AC_CHECK_FUNCS_ONCE([dup2])
15 if test $ac_cv_func_dup2 = no; then
19 AC_DEFINE([HAVE_DUP2], [1], [Define to 1 if you have the 'dup2' function.])
21 if test $HAVE_DUP2 = 1; then
22 AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
24 AC_LANG_PROGRAM([[#include <unistd.h>
28 #ifdef HAVE_GETDTABLESIZE
29 int bad_fd = getdtablesize ();
34 if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
40 if (fcntl (1, F_GETFD) != FD_CLOEXEC)
44 if (dup2 (0, 0) != -1)
46 /* Many gnulib modules require POSIX conformance of EBADF. */
47 if (dup2 (2, bad_fd) == -1 && errno != EBADF)
49 /* Flush out some cygwin core dumps. */
50 if (dup2 (2, -1) != -1 || errno != EBADF)
57 [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
59 mingw*) # on this platform, dup2 always returns 0 for success
60 gl_cv_func_dup2_works="guessing no" ;;
61 cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
62 gl_cv_func_dup2_works="guessing no" ;;
63 linux*) # On linux between 2008-07-27 and 2009-05-11, dup2 of a
64 # closed fd may yield -EBADF instead of -1 / errno=EBADF.
65 gl_cv_func_dup2_works="guessing no" ;;
67 # on AIX 7.1 and FreeBSD 6.1, dup2 (1,toobig) gives EMFILE,
69 gl_cv_func_dup2_works="guessing no" ;;
70 haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
71 gl_cv_func_dup2_works="guessing no" ;;
72 *) gl_cv_func_dup2_works="guessing yes" ;;
75 case "$gl_cv_func_dup2_works" in
79 AC_CHECK_FUNCS([setdtablesize])
83 dnl Replace dup2() for supporting the gnulib-defined fchdir() function,
84 dnl to keep fchdir's bookkeeping up-to-date.
85 m4_ifdef([gl_FUNC_FCHDIR], [
87 if test $HAVE_FCHDIR = 0; then
88 if test $HAVE_DUP2 = 1; then
95 # Prerequisites of lib/dup2.c.
96 AC_DEFUN([gl_PREREQ_DUP2], [])