Re: Prothon bug: strange interaction between self and add_

When I first tried to run it, I couldn't make it fail.  Then I saw it fail
once on the very last iteration of the loop.  That made me think that it had
to do with the memory manager thread starting up, because I'm running on a
very fast dual opteron workstation and your whole loop is finishing before
the memory manager even gets going.

So I turned on the thread debug flag which prints out when threads start and
stop and also turns on extra background torture threads that just read and
write objects to slow things down.  Sure enough, your problem showed up
immediately after the memory manager started.  So the problem has to do with
an interaction with the garbage collector.  I have some kind of bug where
I'm deleting an object you are still using.

I should find my bug soon...