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

Eliot Miranda eliot.miranda at gmail.com
Mon Dec 3 19:09:54 UTC 2012

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.

>  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

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