On Wed, Jan 25, 2017 at 11:35 AM, Norbert Hartl <norbert@hartl.name> wrote:
Does anyone know the state of immutability support in vm and image? The latest vm downloadable is compiled with

IMMUTABILITY=1

(Esteban said that). When I open a pharo6 image with this VM and do:

ASUser new
�� �� �� �� setIsReadOnlyObject: true;
�� �� �� �� name: 'foo'

with

ASUser>>#name: arg1
�� �� �� �� name := arg1

I don't get an exception. Is there something missing or am I not understanding?

Hi Norbert,

Thank you very much for looking read-only objects.

When mutating an instance variable, the VM triggers a call-back that by default does nothing. In your case, running your code does not raise an exception but the object should not be modified either. If you want an exception, you need to change the call-back code, i.e., the method Object>>#attemptToAssign: value withIndex: index. For example, you could write:

Object>>#attemptToAssign: value withIndex: index��
| process |
self notify: 'object changed !'.
process := Processor activeProcess.
[ process suspendedContext: process suspendedContext sender ] forkAt: Processor activePriority + 1.
Processor yield.

Then, your code should open a notification window with 'object changed', and proceeding keeps running the code without mutating the object.

One needs to build a ModificationTracker framework on top of the VM support I introduced. Multiple things are required, like default behavior in this call-back and in primitive failure code. I am willing to support and help anyone willing to build such a framework, but I won't build it myself.

If you have any other questions or if you find bug don't hesitate to ask further questions

Best,

PS: Make sure "Smalltalk vm supportsWriteBarrier" answers true in your system, if this is not the case it means the VM does not support read-only objects.

Clement




��

Norbert