[Vm-dev] Immutability bit? Eliot?

[Göran Krampe]

Hi VM gurus!

I just responded to a persistence thread on the seaside-list and it 
occurred to me that I should ask you guys - especially Eliot I guess - 
will the new VM have support for detecting object modification?

...and oh, when do we get the new awesome VM? I am doing reload on 
mirandabanda every day but no luck so far... :) :)

Cees de Groot explained a technique (a long while back) using an 
immutability bit on objects - combined with some Exception being 
signalled when an immutable object is about to be modified. This way you 
get both support for immutable objects AND "dirty marking" because you 
can always catch the Exception, add the object as "dirty" in a pool, and 
then resume.

Especially for all the persistence solutions out there this would be 
great to have - and would eliminate trickery like WriteBarrier:

http://map.squeak.org/packagebyname/writebarrier

regards, Göran