On Sat, Aug 27, 2011 at 12:30 AM, Igor Stasenko siguctua@gmail.com wrote:

On 25 August 2011 23:26, Michael van der Gulik mikevdg@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.

Thanks.

Sorry about that email - my hand slipped and it got sent before I was finished.

Michael.

On 31 August 2011 12:50, Mariano Martinez Peck marianopeck@gmail.com wrote:

On Fri, Aug 26, 2011 at 2:30 PM, Igor Stasenko siguctua@gmail.com wrote:

...

On 25 August 2011 23:26, Michael van der Gulik mikevdg@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