Method valid

include/dmlc/concurrentqueue.h:616–616

A token is always valid unless: 1) Memory allocation failed during construction 2) It was moved via the move constructor (Note: assignment does a swap, leaving both potentially valid) 3) The associated queue was destroyed Note that if valid() returns true, that only indicates that the token is valid for use with a specific queue, but not which one; that's up to the user to track.

  // that the token is valid for use with a specific queue,
  // but not which one; that's up to the user to track.
  inline bool valid() const { return producer != nullptr; }

  ~ProducerToken()
  {