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