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# serial 6
# See if we need to provide linkat replacement.
dnl Copyright (C) 2009-2012 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.
# Written by Eric Blake.
AC_DEFUN([gl_FUNC_LINKAT],
[
AC_REQUIRE([gl_FUNC_OPENAT])
AC_REQUIRE([gl_FUNC_LINK_FOLLOWS_SYMLINK])
AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CHECK_FUNCS_ONCE([linkat symlink])
AC_CHECK_HEADERS_ONCE([sys/param.h])
if test $ac_cv_func_linkat = no; then
HAVE_LINKAT=0
else
AC_CACHE_CHECK([whether linkat(,AT_SYMLINK_FOLLOW) works],
[gl_cv_func_linkat_follow],
[rm -rf conftest.f1 conftest.f2
touch conftest.f1
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#include <fcntl.h>
#include <unistd.h>
#ifdef __linux__
/* Linux added linkat in 2.6.16, but did not add AT_SYMLINK_FOLLOW
until 2.6.18. Always replace linkat to support older kernels. */
choke me
#endif
]], [return linkat (AT_FDCWD, "conftest.f1", AT_FDCWD, "conftest.f2",
AT_SYMLINK_FOLLOW);])],
[gl_cv_func_linkat_follow=yes],
[gl_cv_func_linkat_follow="need runtime check"])
rm -rf conftest.f1 conftest.f2])
AC_CACHE_CHECK([whether linkat handles trailing slash correctly],
[gl_cv_func_linkat_slash],
[rm -rf conftest.a conftest.b conftest.c conftest.d
AC_RUN_IFELSE(
[AC_LANG_PROGRAM(
[[#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
]],
[[int result;
int fd;
/* Create a regular file. */
fd = open ("conftest.a", O_CREAT | O_EXCL | O_WRONLY, 0600);
if (fd < 0)
return 1;
if (write (fd, "hello", 5) < 5)
return 2;
if (close (fd) < 0)
return 3;
/* Test whether hard links are supported on the current
device. */
if (linkat (AT_FDCWD, "conftest.a", AT_FDCWD, "conftest.b",
AT_SYMLINK_FOLLOW) < 0)
return 0;
result = 0;
/* Test whether a trailing "/" is treated like "/.". */
if (linkat (AT_FDCWD, "conftest.a/", AT_FDCWD, "conftest.c",
AT_SYMLINK_FOLLOW) == 0)
result |= 4;
if (linkat (AT_FDCWD, "conftest.a", AT_FDCWD, "conftest.d/",
AT_SYMLINK_FOLLOW) == 0)
result |= 8;
return result;
]])],
[gl_cv_func_linkat_slash=yes],
[gl_cv_func_linkat_slash=no],
[# Guess yes on glibc systems, no otherwise.
case "$host_os" in
*-gnu*) gl_cv_func_linkat_slash="guessing yes";;
*) gl_cv_func_linkat_slash="guessing no";;
esac
])
rm -rf conftest.a conftest.b conftest.c conftest.d])
case "$gl_cv_func_linkat_slash" in
*yes) gl_linkat_slash_bug=0 ;;
*) gl_linkat_slash_bug=1 ;;
esac
if test "$gl_cv_func_linkat_follow" != yes \
|| test $gl_linkat_slash_bug = 1; then
REPLACE_LINKAT=1
AC_DEFINE_UNQUOTED([LINKAT_TRAILING_SLASH_BUG], [$gl_linkat_slash_bug],
[Define to 1 if linkat fails to recognize a trailing slash.])
fi
fi
])
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