On 6 Sep 2018, at 23:35, Petr Fischer via Pharo-users <pharo-users@lists.pharo.org> wrote:

From: Petr Fischer <petr.fischer@me.com>

Subject: adding instance variables (data) to the Object class

Date: 6 September 2018 at 23:35:26 CEST

To: pharo-users@lists.pharo.org

Hello! Weird question: why I can't add instance variables to the Object class (for example "oid" or something else)? Is it due to some internal (and different) VM "class layouts"?

Or - can I inject my own information to all existing objects (any class)?

Behavior is a subclass of Object, too. So that means that you would add a ivar to all the classes, but for the VM an object can only be a class that has three ivars, and those

are accessed by offset. So if you add an ivar, you shift the offset ���> problem.

As for ���I want to add object specific state���: it would be nice to add an easy to use (and efficient) mechanism to do it.

Marcus