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-rw-r--r--gl/m4/dup2.m4105
1 files changed, 105 insertions, 0 deletions
diff --git a/gl/m4/dup2.m4 b/gl/m4/dup2.m4
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1#serial 27
2dnl Copyright (C) 2002, 2005, 2007, 2009-2023 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], [])