[Vm-dev] Re: [squeak-dev] New Cog VMs available

[Eliot Miranda]

On Mon, Dec 3, 2012 at 11:39 AM, Blake McBride <blake at mcbride.name> wrote:

>
> Hello Eliot,
>
> On Mon, Dec 3, 2012 at 1:09 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:
>
>>
>> Hi Blake,
>>
>> On Mon, Dec 3, 2012 at 7:10 AM, Blake McBride <blake at mcbride.name> wrote:
>>
>>> Greetings,
>>>
>>> I tried to integrate Squeak to a C based application more than six years
>>> ago.  The project failed because we were not able to have our application
>>> call Squeak, then have Squeak call the application, and then the
>>> application call Squeak again recursively.  An analysis of the Squeak VM
>>> revealed a kernel design consisting of a lot of global variables - quite
>>> unnecessarily.  The unnecessary use of global variables over a localized
>>> structure for example unnecessarily prevented the use of Squeak as an
>>> extension language (unless you had no recursion).  I spent several days
>>> trying to re-structure the Squeak kernel but I kept running into problems
>>> and just ran out of time.
>>>
>>> As a side note, that company I was with ended up making a lot of
>>> investment in Scheme because we were easily able to integrate that language
>>> with our application.  Now, not only is Scheme used heavily within that
>>> company but many of their clients use it too to customize their application.
>>>
>>> This brings me to my question, is COG reentrant?
>>>
>>
>> Yes it is.  It supports call-outs and call-ins.  But currently there is
>> no support for Cog to be packaged as a DLL.  You have to start by calling C
>> from Squeak.
>>
>
> I believe the regular Squeak supports call-outs and call-ins as well.  The
> real question is if it can be done recursively.
>

Yes it can.  The new ThreadedFFI plugin is reentrant, using alloca to stack
allocate space for outgoing arguments and incoming results, permitting
nested callouts and callbacks.


> Can you initialize a new instance of the VM in the middle of a nested
> call-in / callout?
>

That;s not relevant.  Yes one can spawn another VM, but it doesn't share an
address psace or a heap.  But within the single address space and single
heap one can nest call-outs and call-backs.


> Can an instance be cloned?  Destroyed?
>

Effectively yes.  One way is snapshot and start up of that snapshot.  But I
think the OSProcessPlugin supports fork.  However, IMO that's unrelated to
the reentrant FFI.


> Thanks.
>
> Blake
>

cheers!


>
>
>
>>
>>
>>
>>
>>>  If not, as the author of COG, I would think it relatively easy to
>>> restructure it to be so.  Such a design capability can make a huge
>>> difference to COG's acceptance to many.  It may even be the reason to
>>> switch to COG.
>>>
>>
>> Yes indeed.   The issue is of course funding to spend the time to make
>> the necessary changes.
>>
>>
>>> Just sharing some thoughts.  Thanks.
>>>
>>> Blake McBride
>>>
>>> On Sun, Dec 2, 2012 at 7:55 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:
>>>
>>>> ...in http://www.mirandabanda.org/files/Cog/VM/VM.r2628.
>>>>
>>>> These fix a bug with pc mapping that could cause the Vm to crash on
>>>> simple loops containing arithmetic on constants (e.g. 1 to: 20 do: [:i|
>>>> 1=1]).  They also cause the instantiation primitives to pop all their
>>>> arguments rather than assume their argument count is 0 or 1.  More change
>>>> info available in the directory.
>>>> --
>>>> best,
>>>> Eliot
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>> --
>> best,
>> Eliot
>>
>>
>>
>
>


-- 
best,
Eliot
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