[Vm-dev] About the image

[stephane ducasse]

>> Hi, I have just began to work at this low level and I have 2 questions:
> 
> Nice. But you need to give us a little more context. What are you trying to do?

Bootstrap 
and shaking/documenting the hidden assumptions on the way.
> 
>> - What is the minimal object structure I should implement from VM perspective?
> 
> Normally you do not have to implement this, as the interpreter is shared between all platforms.

yes we know. Nicolas read the chapter of tim but we wanted to check if this is still up to date.
My original question was more: where can I find the class object VM interpretation (that the first slot should be superclass, format....)
because I remember that we could not add an instance variable into behavior when we did traits.


>> - Where are defined the 3 formats of objects representation?
> 
> Not sure what you mean. ObjectMemory>>formatOf: defines the class format bits in the header. 

Yes we saw that. 

> Or do you mean the 3 header formats? Read the class comment of ObjectMemory.
> 
> Also, there is a nice explanation in section A.1 of Tim's chapter in the NuBlue book:
> 
> http://www.rowledge.org/tim/squeak/assets/OE-Tour.pdf

Another question was where can we get a description of the image format.
I was planning to read the VM C code included the generated one.

Stef