summaryrefslogtreecommitdiff
path: root/gnulib-m4/fcntl.m4
blob: 02b93f8357cda19ec7aeb4e3bd8c9cd968276e7c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
# fcntl.m4 serial 11
dnl Copyright (C) 2009-2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

# For now, this module ensures that fcntl()
# - supports F_DUPFD correctly
# - supports or emulates F_DUPFD_CLOEXEC
# - supports F_GETFD
# Still to be ported to mingw:
# - F_SETFD
# - F_GETFL, F_SETFL
# - F_GETOWN, F_SETOWN
# - F_GETLK, F_SETLK, F_SETLKW
AC_DEFUN([gl_FUNC_FCNTL],
[
  dnl Persuade glibc to expose F_DUPFD_CLOEXEC.
  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
  AC_REQUIRE([AC_CANONICAL_HOST])
  AC_CHECK_FUNCS_ONCE([fcntl])
  if test $ac_cv_func_fcntl = no; then
    gl_REPLACE_FCNTL
  else
    dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target
    dnl haiku alpha 2 F_DUPFD has wrong errno
    AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],
      [gl_cv_func_fcntl_f_dupfd_works],
      [AC_RUN_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <errno.h>
              #include <fcntl.h>
              #include <limits.h>
              #include <sys/resource.h>
              #include <unistd.h>
              ]GL_MDA_DEFINES[
              #ifndef RLIM_SAVED_CUR
              # define RLIM_SAVED_CUR RLIM_INFINITY
              #endif
              #ifndef RLIM_SAVED_MAX
              # define RLIM_SAVED_MAX RLIM_INFINITY
              #endif
            ]],
            [[int result = 0;
              int bad_fd = INT_MAX;
              struct rlimit rlim;
              if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
                  && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
                  && rlim.rlim_cur != RLIM_INFINITY
                  && rlim.rlim_cur != RLIM_SAVED_MAX
                  && rlim.rlim_cur != RLIM_SAVED_CUR)
                bad_fd = rlim.rlim_cur;
              if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
              if (errno != EINVAL) result |= 2;
              if (fcntl (0, F_DUPFD, bad_fd) != -1) result |= 4;
              if (errno != EINVAL) result |= 8;
              /* On OS/2 kLIBC, F_DUPFD does not work on a directory fd */
              {
                int fd;
                fd = open (".", O_RDONLY);
                if (fd == -1)
                  result |= 16;
                else if (fcntl (fd, F_DUPFD, STDERR_FILENO + 1) == -1)
                  result |= 32;

                close (fd);
              }
              return result;]])],
         [gl_cv_func_fcntl_f_dupfd_works=yes],
         [gl_cv_func_fcntl_f_dupfd_works=no],
         [case $host_os in
            aix* | cygwin* | haiku*)
               gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;
            *) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;
          esac])])
    case $gl_cv_func_fcntl_f_dupfd_works in
      *yes) ;;
      *) gl_REPLACE_FCNTL
        AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
          behavior does not match POSIX]) ;;
    esac

    dnl Many systems lack F_DUPFD_CLOEXEC.
    dnl NetBSD 9.0 declares F_DUPFD_CLOEXEC but it works only like F_DUPFD.
    AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
      [gl_cv_func_fcntl_f_dupfd_cloexec],
      [AC_RUN_IFELSE(
         [AC_LANG_SOURCE(
            [[#include <fcntl.h>
              #include <unistd.h>
              int main (int argc, char *argv[])
              {
                if (argc == 1)
                  /* parent process */
                  {
                    if (fcntl (1, F_DUPFD_CLOEXEC, 10) < 0)
                      return 1;
                    return execl ("./conftest", "./conftest", "child", NULL);
                  }
                else
                  /* child process */
                  return (fcntl (10, F_GETFL) < 0 ? 0 : 42);
              }
            ]])
         ],
         [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#ifdef __linux__
/* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
   it to support the semantics on older kernels that failed with EINVAL.  */
choke me
#endif
           ]])],
           [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])
         ],
         [gl_cv_func_fcntl_f_dupfd_cloexec=no],
         [case "$host_os" in
                     # Guess no on NetBSD.
            netbsd*) gl_cv_func_fcntl_f_dupfd_cloexec="guessing no" ;;
            *)       gl_cv_func_fcntl_f_dupfd_cloexec="$gl_cross_guess_normal" ;;
          esac
         ])
      ])
    case "$gl_cv_func_fcntl_f_dupfd_cloexec" in
      *yes) ;;
      *)    gl_REPLACE_FCNTL
            dnl No witness macro needed for this bug.
            ;;
    esac
  fi
  dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
  dnl to keep fchdir's bookkeeping up-to-date.
  m4_ifdef([gl_FUNC_FCHDIR], [
    gl_TEST_FCHDIR
    if test $HAVE_FCHDIR = 0; then
      gl_REPLACE_FCNTL
    fi
  ])
])

AC_DEFUN([gl_REPLACE_FCNTL],
[
  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
  AC_CHECK_FUNCS_ONCE([fcntl])
  if test $ac_cv_func_fcntl = no; then
    HAVE_FCNTL=0
  else
    REPLACE_FCNTL=1
  fi
])