19.4 A Common Multithreading Mistake

Let's assume you have the following application code:

void main()
{
  RWIFtpClient client;
  ...
  // do file transfer processing
  ...
  // incorrect !!!
  client.dataClose();                                        //1
  // instead, use: RWBoolean b = client.dataClose();
  // or assign to IOU and use the callback mechanism
  // or assign to IOU and use the polling mechanism
}

Here a separate thread (say, thread A) is created to handle the dataClose() method invocation. The main thread may exit earlier than thread A, which results in undesirable behavior when thread A exits. This is a common mistake. Though the int library attempts to hide multithread programming issues under the hood, you must be aware of this situation. The solution, provided in the commented-out line below line //1, ensures that thread A exits before the main thread goes out of scope, by forcing the IOU to be redeemed. This blocks the main thread until the dataClose() operation has completed.