Bert Freudenberg wrote
> On Tue, Aug 23, 2016 at 11:21 AM, marcel.taeumel <

> Marcel.Taeumel@

> >
> wrote:
> 
>>
>> Hi, there.
>>
>> It is, unfortunately, not possible to turn back time and rewrite history.
>> ;-)
>>
> 
> ... unless we're dealing with software. Oh wait, we are ;)
> 
> There is several important code that makes excessive use of instVar
>> accesses such as in SystemProgressMorph or HandMorph. Making any change
>> in
>> their class layout while using some of their methods will provoke a
>> strange
>> error. This could only be changed by a VM that keeps old class
>> layouts/schemata around for some longer time until there is no old
>> compiled
>> method on any stack anymore.
> 
> 
> Class layout changes and instance migration is handled fully in the image
> by class ClassBuilder. The VM is not at fault here.
> 
> 
>> Usually, restarting the update process helps here. There is no way to fix
>> that in order to interactively update from 5.0 to 5.1 without any errors.
>>
> 
> We can retroactively change the config map that introduced the problem.
> I'm
> certain it would be possible to fix, but I am not entirely sure it's worth
> the trouble.
> 
> - Bert -

Hi Bert,

the config map will not help, we would have to change numerous MCZs since
point X in time to rewrite history. :) "Oh, would we have always been using
accessors here instead of instVar accessess..."

Best,
Marcel



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