[Vm-dev] questions about a couple of primitives

Florin Mateoc florin.mateoc at gmail.com
Mon Aug 31 22:29:58 UTC 2020

On Mon, Aug 31, 2020 at 6:00 PM Eliot Miranda <eliot.miranda at gmail.com>

> On Mon, Aug 31, 2020 at 2:00 PM Florin Mateoc <florin.mateoc at gmail.com>
> wrote:
>> I think this is especially confusing since the comment says that the
>> primitive always fails, and then the expectation is that the Smalltalk code
>> that follows is executed instead. But that code does not do what the method
>> actually does
> I disagree.  It does exactly what the method does (it *is* the
> implementation of the method) unless the stack is unwound.  Yes, the
> comment could point the reader to Context>>#resume:through: which runs
> the ensure: & ifCurtailed: blocks on unwind.  Bit otherwise ifCurtailed: is
> not somehow magically not executed.  It is what it is ;-)
> As I said earlier,  ifCurtailed: only evaluates its argument if a
> non-local return or exception return is taken and the normal return path is
> not taken.  See Context>>#resume:through: which runs the ensure: &
> ifCurtailed: blocks.
> Can I confirm that your dissatisfaction is with the comment?  Or do you
> really think the ifCurtailed: method does not execute verbatim in the
> absence of unwinds?  If the former, you're welcome to submit an improved
> comment.  If the latter, you're mistaken.

Of course I agree that the ifCurtailed: method does execute verbatim in the
absence of unwind. But the method does not only execute in the absence of
unwinds. So my "dissatisfaction" is not just with the comment. While it
could be somewhat be addressed by a comment, I think this is an instance
where the vm is caught cheating. The shown Smalltalk code is not what gets
executed in the presence of unwinds (as opposed to the code shown in
#ensure: ). The execution of the argument block is hidden inside the vm
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