1# fcntl-o.m4 serial 5
2dnl Copyright (C) 2006, 2009-2017 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
7dnl Written by Paul Eggert.
8
9# Test whether the flags O_NOATIME and O_NOFOLLOW actually work.
10# Define HAVE_WORKING_O_NOATIME to 1 if O_NOATIME works, or to 0 otherwise.
11# Define HAVE_WORKING_O_NOFOLLOW to 1 if O_NOFOLLOW works, or to 0 otherwise.
12AC_DEFUN([gl_FCNTL_O_FLAGS],
13[
14  dnl Persuade glibc <fcntl.h> to define O_NOATIME and O_NOFOLLOW.
15  dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes
16  dnl AC_GNU_SOURCE.
17  m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
18    [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],
19    [AC_REQUIRE([AC_GNU_SOURCE])])
20
21  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
22  AC_CHECK_HEADERS_ONCE([unistd.h])
23  AC_CHECK_FUNCS_ONCE([symlink])
24  AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h],
25    [AC_RUN_IFELSE(
26       [AC_LANG_PROGRAM(
27          [[#include <sys/types.h>
28           #include <sys/stat.h>
29           #if HAVE_UNISTD_H
30           # include <unistd.h>
31           #else /* on Windows with MSVC */
32           # include <io.h>
33           # include <stdlib.h>
34           # defined sleep(n) _sleep ((n) * 1000)
35           #endif
36           #include <fcntl.h>
37           #ifndef O_NOATIME
38            #define O_NOATIME 0
39           #endif
40           #ifndef O_NOFOLLOW
41            #define O_NOFOLLOW 0
42           #endif
43           static int const constants[] =
44            {
45              O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC, O_APPEND,
46              O_NONBLOCK, O_SYNC, O_ACCMODE, O_RDONLY, O_RDWR, O_WRONLY
47            };
48          ]],
49          [[
50            int result = !constants;
51            #if HAVE_SYMLINK
52            {
53              static char const sym[] = "conftest.sym";
54              if (symlink ("/dev/null", sym) != 0)
55                result |= 2;
56              else
57                {
58                  int fd = open (sym, O_WRONLY | O_NOFOLLOW | O_CREAT, 0);
59                  if (fd >= 0)
60                    {
61                      close (fd);
62                      result |= 4;
63                    }
64                }
65              if (unlink (sym) != 0 || symlink (".", sym) != 0)
66                result |= 2;
67              else
68                {
69                  int fd = open (sym, O_RDONLY | O_NOFOLLOW);
70                  if (fd >= 0)
71                    {
72                      close (fd);
73                      result |= 4;
74                    }
75                }
76              unlink (sym);
77            }
78            #endif
79            {
80              static char const file[] = "confdefs.h";
81              int fd = open (file, O_RDONLY | O_NOATIME);
82              if (fd < 0)
83                result |= 8;
84              else
85                {
86                  struct stat st0;
87                  if (fstat (fd, &st0) != 0)
88                    result |= 16;
89                  else
90                    {
91                      char c;
92                      sleep (1);
93                      if (read (fd, &c, 1) != 1)
94                        result |= 24;
95                      else
96                        {
97                          if (close (fd) != 0)
98                            result |= 32;
99                          else
100                            {
101                              struct stat st1;
102                              if (stat (file, &st1) != 0)
103                                result |= 40;
104                              else
105                                if (st0.st_atime != st1.st_atime)
106                                  result |= 64;
107                            }
108                        }
109                    }
110                }
111            }
112            return result;]])],
113       [gl_cv_header_working_fcntl_h=yes],
114       [case $? in #(
115        4) gl_cv_header_working_fcntl_h='no (bad O_NOFOLLOW)';; #(
116        64) gl_cv_header_working_fcntl_h='no (bad O_NOATIME)';; #(
117        68) gl_cv_header_working_fcntl_h='no (bad O_NOATIME, O_NOFOLLOW)';; #(
118         *) gl_cv_header_working_fcntl_h='no';;
119        esac],
120       [case "$host_os" in
121                  # Guess 'no' on native Windows.
122          mingw*) gl_cv_header_working_fcntl_h='no' ;;
123          *)      gl_cv_header_working_fcntl_h=cross-compiling ;;
124        esac
125       ])
126    ])
127
128  case $gl_cv_header_working_fcntl_h in #(
129  *O_NOATIME* | no | cross-compiling) ac_val=0;; #(
130  *) ac_val=1;;
131  esac
132  AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOATIME], [$ac_val],
133    [Define to 1 if O_NOATIME works.])
134
135  case $gl_cv_header_working_fcntl_h in #(
136  *O_NOFOLLOW* | no | cross-compiling) ac_val=0;; #(
137  *) ac_val=1;;
138  esac
139  AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOFOLLOW], [$ac_val],
140    [Define to 1 if O_NOFOLLOW works.])
141])
142