On Mon, Aug 22, 2016 at 02:36:09PM +0200, Bert Freudenberg wrote:
> Seen it, discussed with Marcel but we don't have a good idea yet how to
> work around it.
> 
> The only thing I can think of is to walk up the sender chain and restart
> some context above the one referencing the old instance layout. Maybe an
> exception handler in the updater that restarts updating in this specific
> case?
> 
> - Bert -
> 

I don't see a good place to put an exception handler, at least not without
making things even more complicated than they already are.

It looks like the the direct reference to instance var 'bars' is where we
encounter the problem. Presumably the old code in a block is refering to
an ivar slot in SystemProgressMorph that used to point to the 'vars' array,
but that is now pointing to the 'font' ivar.

And indeed I see now that Marcel found and fixed this issue in Morphic-mt.1198,
so that accessor methods will now be used instead of direct references to
the variables.

But we still have the problem of a SystemProgressMorph evaluating an older
block that was created with an earlier version of the
SystemProgressMorph>>position:label:min:max: method, so the update stream
processing still fails if the update processing was started before
Morphic-mt.1198 was loaded.

A partial workaround is to modify #position:label:min:max: to use an accessor
for 'bars' prior to starting the update processing. This prevents the error
condition that we are discussing here, but unfortunately it also results
in a couple of merge dialogs for the modified methods, so the update still
requires manual intervention.

Dave


> 
> On Sun, Aug 21, 2016 at 10:55 PM, Levente Uzonyi <leves at caesar.elte.hu>
> wrote:
> 
> >
> > Same here. I think the code changes during the update and the old code on
> > the stack causes the problem.
> >
> > Levente
> >
> >
> > On Sun, 21 Aug 2016, Chris Muller wrote:
> >
> >
> >> I've definitely experienced the exact same problem, and got around it
> >> the same way, restarting the method and proceeding.  Very strange.
> >>
> >>
> >> On Sun, Aug 21, 2016 at 3:13 PM, David T. Lewis <lewis at mail.msen.com>
> >> wrote:
> >>
> >>>
> >>> Moving from vm-dev to squeak-dev because it is a trunk update stream
> >>> question.
> >>> Follow ups to squeak-dev please.
> >>>
> >>> Does anyone recognize this problem?
> >>>
> >>> We have an issue in trunk update processing that prevents a full update
> >>> without manual intervention. This does not affect the 5.1 release, but
> >>> it would be good to fix it so that the update from 5.0 to 5.1 can be
> >>> reproduced in a continuous integration test.
> >>>
> >>> To reproduce: Start with Squeak5.0-15113.image, set the update URL
> >>> preference
> >>> to http://source.squeak.org/trunk, and do an "update from server".
> >>>
> >>> The error first appears when beginning to process the update-mt.378.mcm
> >>> update map. The problem is related to updating the progress bar with
> >>> ProgressInitiationException.
> >>>
> >>> When the failure occurs, the debugger (see attached image) seems to
> >>> show an array access being interpreted as if the array was an instance
> >>> of StrikeFont. Per Nicolas' note below, it may be related to showing
> >>> the progress bar while updating it.
> >>>
> >>> I can restart the update process from the debugger from
> >>> SystemProgressMorph>>position:label:min:max: in the stack frame, and the
> >>> update proceeds. The error happens several more times, then at some point
> >>> it seems to go away, so apparently the problem was fixed at some later
> >>> point in the update stream.
> >>>
> >>> Does anyone recognize this problem? Can we work around it by changing one
> >>> or more of the update maps?
> >>>
> >>> Thanks,
> >>> Dave
> >>>
> >>>
> >>> On Fri, Aug 19, 2016 at 10:30:30PM +0200, Nicolas Cellier wrote:
> >>>
> >>>>
> >>>> yes, this is a problem I encountered both in 32 and 64 bits squeak while
> >>>> updating.
> >>>>
> >>>> I think it's related to showing the progress bar while updating the
> >>>> progress bar. It's a Squeak trunk update problem, not a VM problem.
> >>>>
> >>>> If some class layout change, but some block is still active (yeah, did
> >>>> you
> >>>> see how many blocks we traverse just to change display of a bar...),
> >>>> then
> >>>> the old block has invalid inst var offsets (offsets to the old object
> >>>> that
> >>>> now has become a new object with new layout).
> >>>>
> >>>> In an interactive image, just close the debugger and relaunch the
> >>>> update.
> >>>> In an headless automated process, well... We should have fixed the
> >>>> update
> >>>> or start from a newer artifact...
> >>>>
> >>>> 2016-08-19 21:32 GMT+02:00 tim Rowledge <tim at rowledge.org>:
> >>>>
> >>>>>
> >>>>> I just tried running the vmmaker-build script on my iMac with weirdly
> >>>>> bad
> >>>>> results.
> >>>>>
> >>>>> The vm it downloads is the CogSpur.app-16.18.3692 version. Whilst
> >>>>> trying
> >>>>> to do the update part of the process I had several *very* odd failures
> >>>>> where an object in a block was mistaken for nil during a message send.
> >>>>> For
> >>>>> example in a progress bar update (which I can???t provide a log for
> >>>>> since the
> >>>>> log got overwritten later) a line
> >>>>> (bars at: index)
> >>>>> lead to a nil is not indexable halt. Yet in inspecting the prior
> >>>>> stackframe the bars object was a perfectly normal array of progress
> >>>>> bars. A
> >>>>> similar but not identical problem happened during another attempt.
> >>>>>
> >>>>> Attempting to filein the BuildSqueakSpurTrunkVMMaker.st file failed
> >>>>> when
> >>>>> the vm exploded with no visible log.
> >>>>>
> >>>>> Now I???m attempting to repeat that with a new 5.1rc1 vm & already up
> >>>>> to
> >>>>> date 5.1rc1 image. Which has sorta-worked, in a rather odd manner. It
> >>>>> got
> >>>>> to the final save and quit but when I start the supposedly prepared
> >>>>> image
> >>>>> there is a problem with it trying to filein that file. I can???t tell
> >>>>> right
> >>>>> now if it relates to the manual filein I started or if something got
> >>>>> added
> >>>>> as a deferred action? Or maybe it???s a side-effect of the filein
> >>>>> having a
> >>>>> save & quit? Not come across this before.
> >>>>>
> >>>>>
> >>>>>
> >>>>> So far as I can tell it did complete the filein, so maybe all is well.
> >>>>>
> >>>>>
> >>>
> >>

>