AC_CHECK_FUNCS(vsyslog setlinebuf mktime ftruncate chsize rename)
AC_CHECK_FUNCS(waitpid wait4 strlcpy strlcat initgroups memmove strdup)
AC_CHECK_FUNCS(pread pwrite strndup strcasestr strtok_r mkdtemp dup2 dprintf vdprintf)
-AC_CHECK_FUNCS(isatty chown lchown link readlink symlink realpath)
+AC_CHECK_FUNCS(isatty chown lchown link readlink symlink realpath fdatasync)
AC_HAVE_DECL(setresuid, [#include <unistd.h>])
AC_HAVE_DECL(setresgid, [#include <unistd.h>])
AC_HAVE_DECL(errno, [#include <errno.h>])