Question

Is it safe to override Free method? I’m asking because I would like to use something like this. I know it’s very ugly to use TerminateThread, but in my case it’s very critical to kill the process with all its threads immediately.

I’ve seen the __free method declared in System.pas, but I don’t know if it has something to do with the TObject.Free method and that’s the reason why I’m asking if it’s safe.

type
  TMyThread = class(TThread)
  private
    destructor Destroy; override;
  public
    procedure Execute; override;
    constructor Create;
    procedure Free(const Force: Boolean = False); // is it safe to use this?
  end;

procedure TMyThread.Free(const Force: Boolean = False);
begin
  if not Force then
  begin
    Terminate;
    WaitFor;
  end
  else
    TerminateThread(Handle, 0);

  inherited Free;
end;

destructor TMyThread.Destroy;
begin
  // free resources etc.
  inherited Destroy;
end;

Thank you

Answer 1

You can’t override Free because it’s not virtual. If you define your own Free method it will hide the TObject.Free method (note the compiler warning) if the static type is your class type. This is definitely not a good idea since the object will then never get destroyed.

I don’t see any reason why you want to do that. If you really want to use TerminateThread then just give your thread class another method ForceTerminate, in which you call TerminateThread.