1#serial 25
2dnl Copyright (C) 2002, 2005, 2007, 2009-2020 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(
23           [[#include <errno.h>
24             #include <fcntl.h>
25             #include <limits.h>
26             #include <sys/resource.h>
27             #include <unistd.h>
28             #ifndef RLIM_SAVED_CUR
29             # define RLIM_SAVED_CUR RLIM_INFINITY
30             #endif
31             #ifndef RLIM_SAVED_MAX
32             # define RLIM_SAVED_MAX RLIM_INFINITY
33             #endif
34           ]],
35           [[int result = 0;
36             int bad_fd = INT_MAX;
37             struct rlimit rlim;
38             if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
39                 && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
40                 && rlim.rlim_cur != RLIM_INFINITY
41                 && rlim.rlim_cur != RLIM_SAVED_MAX
42                 && rlim.rlim_cur != RLIM_SAVED_CUR)
43               bad_fd = rlim.rlim_cur;
44             #ifdef FD_CLOEXEC
45               if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
46                 result |= 1;
47             #endif
48             if (dup2 (1, 1) != 1)
49               result |= 2;
50             #ifdef FD_CLOEXEC
51               if (fcntl (1, F_GETFD) != FD_CLOEXEC)
52                 result |= 4;
53             #endif
54             close (0);
55             if (dup2 (0, 0) != -1)
56               result |= 8;
57             /* Many gnulib modules require POSIX conformance of EBADF.  */
58             if (dup2 (2, bad_fd) == -1 && errno != EBADF)
59               result |= 16;
60             /* Flush out some cygwin core dumps.  */
61             if (dup2 (2, -1) != -1 || errno != EBADF)
62               result |= 32;
63             dup2 (2, 255);
64             dup2 (2, 256);
65             /* On OS/2 kLIBC, dup2() does not work on a directory fd.  */
66             {
67               int fd = open (".", O_RDONLY);
68               if (fd == -1)
69                 result |= 64;
70               else if (dup2 (fd, fd + 1) == -1)
71                 result |= 128;
72
73               close (fd);
74             }
75             return result;]])
76        ],
77        [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
78        [case "$host_os" in
79           mingw*) # on this platform, dup2 always returns 0 for success
80             gl_cv_func_dup2_works="guessing no" ;;
81           cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
82             gl_cv_func_dup2_works="guessing no" ;;
83           aix* | freebsd*)
84                   # on AIX 7.1 and FreeBSD 6.1, dup2 (1,toobig) gives EMFILE,
85                   # not EBADF.
86             gl_cv_func_dup2_works="guessing no" ;;
87           haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
88             gl_cv_func_dup2_works="guessing no" ;;
89           *-android*) # implemented using dup3(), which fails if oldfd == newfd
90             gl_cv_func_dup2_works="guessing no" ;;
91           os2*) # on OS/2 kLIBC, dup2() does not work on a directory fd.
92             gl_cv_func_dup2_works="guessing no" ;;
93           *) gl_cv_func_dup2_works="guessing yes" ;;
94         esac])
95      ])
96    case "$gl_cv_func_dup2_works" in
97      *yes) ;;
98      *)
99        REPLACE_DUP2=1
100        AC_CHECK_FUNCS([setdtablesize])
101        ;;
102    esac
103  fi
104  dnl Replace dup2() for supporting the gnulib-defined fchdir() function,
105  dnl to keep fchdir's bookkeeping up-to-date.
106  m4_ifdef([gl_FUNC_FCHDIR], [
107    gl_TEST_FCHDIR
108    if test $HAVE_FCHDIR = 0; then
109      if test $HAVE_DUP2 = 1; then
110        REPLACE_DUP2=1
111      fi
112    fi
113  ])
114])
115
116# Prerequisites of lib/dup2.c.
117AC_DEFUN([gl_PREREQ_DUP2], [])
118