[Vm-dev] Class format

[Igor Stasenko]

On 31 August 2011 12:50, Mariano Martinez Peck <marianopeck at gmail.com> wrote:
>
>
>
> On Fri, Aug 26, 2011 at 2:30 PM, Igor Stasenko <siguctua at gmail.com> wrote:
>>
>> On 25 August 2011 23:26, Michael van der Gulik <mikevdg at gmail.com> wrote:
>> >
>> > Hi.
>> >
>> > Are there really 14 bits free in the Class "format" field?
>> >
>> > The comment for Class>>format:
>> >
>>
>> probably yes.
>> There are 12 bits are for identity hash (and 2 more?),
>> and since every instance has own hash value, these bits in format
>> field of class is not used.
>>
>
> I didn't understand. Why you say there are 14 free bits in the instVar 'format' of a class?  I was checking the method #format: nInstVars variable: isVar words: isWords pointers: isPointers weak: isWeak
>
> and I don't understand that.
>
This information serves as a template header for creating new
instances of a class. And since all object headers contain 12 bits
hash, which are generated during instance creation, it means that at
least those 12 bits
in 'format' value are unused.

> Thanks
>
>
>
> --
> Mariano
> http://marianopeck.wordpress.com
>
>
>



-- 
Best regards,
Igor Stasenko AKA sig.