Drupal是如何避免页面缓存保存Message信息的

function page_get_cache($status_only = FALSE) {
  static $status = FALSE;
  global $user, $base_root;

  if ($status_only) {
    return $status;
  }
  $cache = NULL;

  if (!$user->uid && $_SERVER[‘REQUEST_METHOD‘] == ‘GET‘ && count(drupal_set_message()) == 0 && $_SERVER[‘SERVER_SOFTWARE‘] !== ‘PHP CLI‘) {
    $cache = cache_get($base_root . request_uri(), ‘cache_page‘);

    if (empty($cache)) {
      ob_start();
      $status = TRUE;
    }
  }

  return $cache;
}

 1 function page_set_cache() {
 2   global $user, $base_root;
 3 
 4   if (!$user->uid && $_SERVER[‘REQUEST_METHOD‘] == ‘GET‘ && page_get_cache(TRUE)) {
 5     // This will fail in some cases, see page_get_cache() for the explanation.
 6     if ($data = ob_get_contents()) {
 7       if (variable_get(‘page_compression‘, TRUE) && extension_loaded(‘zlib‘)) {
 8         $data = gzencode($data, 9, FORCE_GZIP);
 9       }
10       ob_end_flush();
11       cache_set($base_root . request_uri(), $data, ‘cache_page‘, CACHE_TEMPORARY, drupal_get_headers());
12     }
13   }
14 }