Deadlock on application close in ReleaseThreadReference

[jpdk]

I run into a situation with Delphi XE 10.2.1 where the code below (VirtualTrees.pas) leaves my application in a deadlock when the application closes:

    if WorkerThread.FRefCount = 0 then
    begin
      with WorkerThread do
      begin
        Terminate;
        SetEvent(WorkEvent);
      end;
      FreeAndNil(WorkerThread);
      CloseHandle(WorkEvent);
    end;

The destructor of WorkerThread (called with FreeAndNil) will not finish and will hang on de Win32 API call EndThread. I'm assuming that this has to do with the WorkEvent that is not properly handled while being destroyed at the same time.

By not calling FreeAndNil(WorkerThread), but instead using FreeOnTerminate, see the code below, fixes this issue for me.

    // Create worker thread, initialize it and send it to its wait loop.
    WorkerThread := TWorkerThread.Create(False);
    WorkerThread.FreeOnTerminate := True;

Cheers,

J.

[joachimmarder]

The suggested change makes sense. Thanks for reporting.