# V6103. Ignored InterruptedException could lead to delayed thread shutdown.

The analyzer found that the 'InterruptedException' in the 'catch' block was ignored. In this case, information about thread interrupts is lost, which can compromise the application's capacity to cancel functions or promptly stop working.

Each thread has an interrupt status – a hidden boolean field that stores information about whether the thread was interrupted or not. To apply this status, you need to call the method 'Thread.interrupt()'. By documentation, any method that can throw 'InterruptedException' clears the interrupt status when this occurs. The method can be, for example, 'Object.wait()', 'Thread.sleep()', or others. If you do not handle the exception properly, the fact of the interrupt will be lost. This will not allow the calling part of the program to react to the execution cancellation. However, there may be cases where the interrupt status will not be reset when 'InterruptedException' is thrown. For example, a custom interrupt implementation, methods of third-party libraries. It is not recommended to count on these scenarios.

There are options to ensure that information about thread interrupts is not lost. When catching 'InterruptedException' you should either set the interrupt flag using 'Thread.interrupt()' or throw the caught exception further without wrapping it in any other. If interrupt handling is meaningless, this exception must not be caught.

Consider an erroneous code example from a real application:

    public void disconnect()
    {
      ....
      try
      {
        sendThread.join();
      }
      catch (InterruptedException ex)
      {
        LOG.warn("....", ex);
      }
      ....
    }

The correct code must look like this:

    public void disconnect()
    {
      ....
      try
      {
        sendThread.join();
      }
      catch (InterruptedException ex)
      {
        Thread.currentThread().interrupt();
        LOG.warn("....", ex);
      }
      ....
    }

This diagnostic is classified as:

CWE-391