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# fcntl-o.m4 serial 4
dnl Copyright (C) 2006, 2009-2016 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.
dnl Written by Paul Eggert.
# Test whether the flags O_NOATIME and O_NOFOLLOW actually work.
# Define HAVE_WORKING_O_NOATIME to 1 if O_NOATIME works, or to 0 otherwise.
# Define HAVE_WORKING_O_NOFOLLOW to 1 if O_NOFOLLOW works, or to 0 otherwise.
AC_DEFUN([gl_FCNTL_O_FLAGS],
[
dnl Persuade glibc <fcntl.h> to define O_NOATIME and O_NOFOLLOW.
dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes
dnl AC_GNU_SOURCE.
m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
[AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],
[AC_REQUIRE([AC_GNU_SOURCE])])
AC_CHECK_HEADERS_ONCE([unistd.h])
AC_CHECK_FUNCS_ONCE([symlink])
AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h],
[AC_RUN_IFELSE(
[AC_LANG_PROGRAM(
[[#include <sys/types.h>
#include <sys/stat.h>
#if HAVE_UNISTD_H
# include <unistd.h>
#else /* on Windows with MSVC */
# include <io.h>
# include <stdlib.h>
# defined sleep(n) _sleep ((n) * 1000)
#endif
#include <fcntl.h>
#ifndef O_NOATIME
#define O_NOATIME 0
#endif
#ifndef O_NOFOLLOW
#define O_NOFOLLOW 0
#endif
static int const constants[] =
{
O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC, O_APPEND,
O_NONBLOCK, O_SYNC, O_ACCMODE, O_RDONLY, O_RDWR, O_WRONLY
};
]],
[[
int result = !constants;
#if HAVE_SYMLINK
{
static char const sym[] = "conftest.sym";
if (symlink ("/dev/null", sym) != 0)
result |= 2;
else
{
int fd = open (sym, O_WRONLY | O_NOFOLLOW | O_CREAT, 0);
if (fd >= 0)
{
close (fd);
result |= 4;
}
}
if (unlink (sym) != 0 || symlink (".", sym) != 0)
result |= 2;
else
{
int fd = open (sym, O_RDONLY | O_NOFOLLOW);
if (fd >= 0)
{
close (fd);
result |= 4;
}
}
unlink (sym);
}
#endif
{
static char const file[] = "confdefs.h";
int fd = open (file, O_RDONLY | O_NOATIME);
if (fd < 0)
result |= 8;
else
{
struct stat st0;
if (fstat (fd, &st0) != 0)
result |= 16;
else
{
char c;
sleep (1);
if (read (fd, &c, 1) != 1)
result |= 24;
else
{
if (close (fd) != 0)
result |= 32;
else
{
struct stat st1;
if (stat (file, &st1) != 0)
result |= 40;
else
if (st0.st_atime != st1.st_atime)
result |= 64;
}
}
}
}
}
return result;]])],
[gl_cv_header_working_fcntl_h=yes],
[case $? in #(
4) gl_cv_header_working_fcntl_h='no (bad O_NOFOLLOW)';; #(
64) gl_cv_header_working_fcntl_h='no (bad O_NOATIME)';; #(
68) gl_cv_header_working_fcntl_h='no (bad O_NOATIME, O_NOFOLLOW)';; #(
*) gl_cv_header_working_fcntl_h='no';;
esac],
[gl_cv_header_working_fcntl_h=cross-compiling])])
case $gl_cv_header_working_fcntl_h in #(
*O_NOATIME* | no | cross-compiling) ac_val=0;; #(
*) ac_val=1;;
esac
AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOATIME], [$ac_val],
[Define to 1 if O_NOATIME works.])
case $gl_cv_header_working_fcntl_h in #(
*O_NOFOLLOW* | no | cross-compiling) ac_val=0;; #(
*) ac_val=1;;
esac
AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOFOLLOW], [$ac_val],
[Define to 1 if O_NOFOLLOW works.])
])
........