1#serial 20
2dnl Copyright (C) 2002, 2005, 2007, 2009-2014 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7AC_DEFUN([gl_FUNC_DUP2],
8[
9  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10  AC_REQUIRE([AC_CANONICAL_HOST])
11  m4_ifdef([gl_FUNC_DUP2_OBSOLETE], [
12    AC_CHECK_FUNCS_ONCE([dup2])
13    if test $ac_cv_func_dup2 = no; then
14      HAVE_DUP2=0
15    fi
16  ], [
17    AC_DEFINE([HAVE_DUP2], [1], [Define to 1 if you have the 'dup2' function.])
18  ])
19  if test $HAVE_DUP2 = 1; then
20    AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
21      [AC_RUN_IFELSE([
22         AC_LANG_PROGRAM([[#include <unistd.h>
23#include <fcntl.h>
24#include <errno.h>]],
25           [int result = 0;
26#ifdef FD_CLOEXEC
27            if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
28              result |= 1;
29#endif
30            if (dup2 (1, 1) == 0)
31              result |= 2;
32#ifdef FD_CLOEXEC
33            if (fcntl (1, F_GETFD) != FD_CLOEXEC)
34              result |= 4;
35#endif
36            close (0);
37            if (dup2 (0, 0) != -1)
38              result |= 8;
39            /* Many gnulib modules require POSIX conformance of EBADF.  */
40            if (dup2 (2, 1000000) == -1 && errno != EBADF)
41              result |= 16;
42            /* Flush out some cygwin core dumps.  */
43            if (dup2 (2, -1) != -1 || errno != EBADF)
44              result |= 32;
45            dup2 (2, 255);
46            dup2 (2, 256);
47            return result;
48           ])
49        ],
50        [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
51        [case "$host_os" in
52           mingw*) # on this platform, dup2 always returns 0 for success
53             gl_cv_func_dup2_works="guessing no" ;;
54           cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
55             gl_cv_func_dup2_works="guessing no" ;;
56           linux*) # On linux between 2008-07-27 and 2009-05-11, dup2 of a
57                   # closed fd may yield -EBADF instead of -1 / errno=EBADF.
58             gl_cv_func_dup2_works="guessing no" ;;
59           freebsd*) # on FreeBSD 6.1, dup2(1,1000000) gives EMFILE, not EBADF.
60             gl_cv_func_dup2_works="guessing no" ;;
61           haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
62             gl_cv_func_dup2_works="guessing no" ;;
63           *) gl_cv_func_dup2_works="guessing yes" ;;
64         esac])
65      ])
66    case "$gl_cv_func_dup2_works" in
67      *yes) ;;
68      *)
69        REPLACE_DUP2=1
70        AC_CHECK_FUNCS([setdtablesize])
71        ;;
72    esac
73  fi
74  dnl Replace dup2() for supporting the gnulib-defined fchdir() function,
75  dnl to keep fchdir's bookkeeping up-to-date.
76  m4_ifdef([gl_FUNC_FCHDIR], [
77    gl_TEST_FCHDIR
78    if test $HAVE_FCHDIR = 0; then
79      if test $HAVE_DUP2 = 1; then
80        REPLACE_DUP2=1
81      fi
82    fi
83  ])
84])
85
86# Prerequisites of lib/dup2.c.
87AC_DEFUN([gl_PREREQ_DUP2], [])
88