Comment 9 for bug 741387

  gtk/updateiconcache.c:1531

    if (!validate_file (tmp_cache_path))
    {
      g_printerr (_("The generated cache was invalid.\n"));
      /*g_unlink (tmp_cache_path);*/
      exit (1);
    }

   …

  gtk/updateiconcache.c:1398
  validate_file (const gchar *file)
  {
  …
    if (!_gtk_icon_cache_validate (&info))
    {

  gtk/gtkiconcachevalidator.c:371

    371 /**
    372 * _gtk_icon_cache_validate:
    373 * @info: a CacheInfo structure
    374 *
    375 * Validates the icon cache passed in the @cache and
    376 * @cache_size fields of the @info structure. The
    377 * validator checks that offsets specified in the
    378 * cache do not point outside the mapped area, that
    379 * strings look reasonable, and that pixbufs can
    380 * be deserialized. The amount of validation can
    381 * be controlled with the @flags field.
    382 *
    383 * Return value: %TRUE if the cache is valid
    384 */
    385 gboolean
    386 _gtk_icon_cache_validate (CacheInfo *info)

  /**
   * _gtk_icon_cache_validate:
   * @info: a CacheInfo structure
   *
   * Validates the icon cache passed in the @cache and
   * @cache_size fields of the @info structure. The
   * validator checks that offsets specified in the
   * cache do not point outside the mapped area, that
   * strings look reasonable, and that pixbufs can
   * be deserialized. The amount of validation can
   * be controlled with the @flags field.
   *
   * Return value: %TRUE if the cache is valid
   */
  gboolean
  _gtk_icon_cache_validate (CacheInfo *info)
  {

nb. it could also be interaction with:

  debian/patches/060_ignore-random-icons.patch