[squeak-dev] process-faithful debugging?

Igor Stasenko siguctua at gmail.com
Fri Jul 17 01:44:29 UTC 2009

2009/7/17 Eliot Miranda <eliot.miranda at gmail.com>:
> Hi All,
>     does anyone have a neat hack to make Processor activeProcess answer
> what's expected in the context of the debugger?  i.e. anyone made the Squeak
> debugger answer the process being debugger when Processor activeProcess is
> stepped over or through, rather than the debugger process, or made the
> debugger run as the process being debugged rather than its own?

Very good question, Eliot!
I always wondered, why to access the active process we use global - Processor.
A running process is closely related to contexts, and therefore it
would be more correct to ask a context about it's process rather than

thisContext process
instead of
Processor activeProcess.

I have an idea about this.
Its hacky and will require VM modifications - but having much benefits IMO :)
I think this is most clean & lean way to deal with process-local
storage in smalltalk:

- add 3 __class instance__ variables to ContextPart:
  - methodContextClass
  - blockContextClass
  - process

Now, when creating a new process , create a two anonymous subclasses
of MethodContext and BlockContext,
and fill these ivars in each one appropriately.

Then, all contexts which allocated for given process should use these
anonymous subclasses as their classes.
For VM this means, that when it allocating new context, it should copy
the class reference from caller context (or read a
   methodContextClass or blockContextClass ivars in caller context
class object).

And then accessing a process ( or process-local storage) is trivial & quick:

   ^ self class process

> Eliot

Best regards,
Igor Stasenko AKA sig.

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