[fpc-devel] Threading in FPC and bug report

[Florian Klaempfl]

Pedro Lopez-Cabanillas wrote:
> Hi,
> 
> I would like to ask politely for some elaboration about the closing comment on 
> this bug report: http://www.freepascal.org/mantis/view.php?id=5940
> 
> It was opened one year ago, when I was testing the FPC release 2.0.0, but the 
> situation didn't change too much in all this time. 
> 
> I know that it is not a real and perfect test case, but the program shows some  
> facts.
> 
> 1. When it is compiled with FPC under Linux, it behaves different than when 
> Kylix 3 is used. It doesn't need a thread.waitfor under Kylix to work 
> properly.

Multi threaded programs show often undeterministic behaviour and a slight
implementation difference makes ugly things like race conditions pop up.

> 2. The program exists with an ugly runtime error, when it is compiled with 
> FPC.

Yes, because imo the code contains a racing condition: under certain conditions,
the main thread might end and close all input/output handles etc. while the
thread executing MyThread.Execute might be still running. The code doesn't
ensure that the child thread exits before the main thread stops.