// in order to update them as appropriate.
  auto new_entry = std::make_shared<Block>();
  lru_list_.push_front(key);
  lra_list_.push_front(key);
  new_entry->lru_iterator = lru_list_.begin();
  new_entry->lra_iterator = lra_list_.begin();
  new_entry->timestamp = timer_seconds_();
  block_map_.emplace(std::make_pair(key, new_entry));
  return new_entry;
}

                                             TF_DataType value);
// If the number of dimensions is unknown, `num_dims` must be set to
// -1 and `dims` can be null.  If a dimension is unknown, the
// corresponding entry in the `dims` array must be -1.
TF_CAPI_EXPORT extern void TFE_OpSetAttrShape(TFE_Op* op, const char* attr_name,
                                              const int64_t* dims,

  void RemoveFile_Locked(const std::string& filename)
      ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);

  /// Remove the block `entry` from the block map and LRU list, and update the
  /// cache size accordingly.
  void RemoveBlock(BlockMap::iterator entry) ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_);

  /// The cache pruning thread that removes files with expired blocks.

// gradients available initially).
//
// Then we repeatedly pop an entry from the stack, run its backprop, and update
// the gradients of its inputs. Once we have computed all gradients for a single
// input we can mark this input as done, and this can trigger adding an entry to
// the stack if all outputs of that entry are now done.
//
// When the stack is empty we have gradients for all tensors we're interested

+#define UT_LINESIZE	32
+#define UT_NAMESIZE	32
+#define UT_HOSTSIZE	256
 
 
+/* The structure describing an entry in the database of
+   previous logins.  */
 struct lastlog
   {
     time_t ll_time;
@@ -36,12 +38,16 @@ struct lastlog
     char ll_host[UT_HOSTSIZE];
   };
 
+/* The structure describing an entry in the user accounting database.  */
 struct utmp
   {
-    char ut_line[UT_LINESIZE];