the mooc is a mine for Pharo bugs...
In the video at 6:12, we have a new method sending the new message. I've
made similar mistakes and Pharo does lock up, but then the operating
system (Windows 10) kills the Pharo VM. (Or perhaps there's a bug in
Pharo itself which just crashes the whole VM. I can't tell the difference.)
Is that because it's a memory leak? Does the VM have a fixed amount of
memory available, or can it request more from the OS?
Is there a way to recover from this error without killing the whole VM?
Most GUI systems I've used have at least two threads so that pushing a
button doesn't lock up the whole UI if the task takes a while. Does
Pharo always lock up for long-running tasks, or does it have some kind
of threading ability too? If a background thread gets in an infinite
loop, how do you kill it without killing the whole VM?
here was my answer
The real answer is a bit more complex so I may write some
approximations: - what you did a really tight loops that fills up the
memory really fast. - depending on the OS the VM can or not (in its
current state) allocate more. In some versions it has to preallocate.
"Most GUI systems I've used have at least two threads so that pushing a
button doesn't lock up the whole UI if the task takes a while. Does
Pharo always lock up for long-running tasks, or does it have some kind
of threading ability too? If a background thread gets in an infinite
loop, how do you kill it without killing the whole VM?"
Pharo has a full model for concurrent programming. Check the class
Process, Semaphore. We have some stress tests that create thousands of
threads without problems. You have also package such TaskIt to schedule
tasks
Now the actual problem that you see and that I would love to see fix in
the future is that the code you execute is run in the UI thread
(arghhhhh) It is still like that for historical reason. We should do one
pass on that but this is not that simple because it will raise a couple
of bugs.
Now I think that it would be great if people from the pharo core would
browse in diagonal the problems that students
encounter because there are our real customers and they show many
problems of the system. Especially the ones we do not see anymore.
