2010/3/4 Levente Uzonyi <leves at elte.hu>:
> On Thu, 4 Mar 2010, Nicolas Cellier wrote:
>
>> 2010/3/4 Levente Uzonyi <leves at elte.hu>:
>>>
>>> On Thu, 4 Mar 2010, Nicolas Cellier wrote:
>>>
>>>> 2010/3/3 Levente Uzonyi <leves at elte.hu>:
>>>>>
>>>>> On Wed, 3 Mar 2010, Andreas Raab wrote:
>>>>>
>>>>>> On 3/3/2010 2:07 PM, Levente Uzonyi wrote:
>>>>>>>
>>>>>>> On Wed, 3 Mar 2010, Igor Stasenko wrote:
>>>>>>>>
>>>>>>>> i don't get it. Just before that, you said: ' I'd expect it to be
>>>>>>>> evaluated no matter what happens.' ?
>>>>>>>> But now you saying that it may not be executed in some conditions
>>>>>>>> (when user pressing abandon button, causing process to be
>>>>>>>> terminated).
>>>>>>>
>>>>>>> It's simple: don't terminate process X from another process if
>>>>>>> process
>>>>>>> X
>>>>>>> is executing a termiation block (aka #ensure: block). Or if you
>>>>>>> terminate it, make sure that the execution of the block will continue
>>>>>>> somehow (I don't care how).
>>>>>>
>>>>>> You're missing Igors point which is that in his example the halt /
>>>>>> Transcript *was* in the ensure block and as a result you're
>>>>>> contradicting
>>>>>> yourself here. Let's go back to Igor's example:
>>>>>>
>>>>>> [self boom ] ensure: [ self halt. Transcript show: 'boom']
>>>>>>
>>>>>> The halt is inside the ensure block. If you terminate the process from
>>>>>> the
>>>>>> debugger, it would be logical from your statement that the Transcript
>>>>>> message would be executed - after all it's " executing a termiation
>>>>>> block
>>>>>> (aka #ensure: block)" and so it can't be terminated by your reasoning.
>>>>>> However, when Igor was pointing this out you replied with "I didn't
>>>>>> say
>>>>>> that. I said evaluate it the same way as normal code." which is
>>>>>> inconsistent
>>>>>> with the other statement.
>>>>>
>>>>> That shows my lack of knowledge about how the debugger works.
>>>>>
>>>>>>
>>>>>>> I think every user of #ensure: expects that the termination blocks
>>>>>>> are
>>>>>>> executed even if the process which is executing the receiver of
>>>>>>> #ensure:
>>>>>>> is terminated. And it actually happens in all but this case.
>>>>>>
>>>>>> The question of terminating processes is always tricky. I don't think
>>>>>> that
>>>>>> your proposal would actually work in practice - it could easily result
>>>>>> in
>>>>>> processes that cannot be terminated due to a simple bug in an ensure
>>>>>> block.
>>>>>> Personally, I'd rather say that the more useful behavior would be
>>>>>> something
>>>>>> along the lines of saying that process termination either skips the
>>>>>> current
>>>>>> ensure block (assuming there's a bug and it should get the heck out of
>>>>>> it
>>>>>> but try to evaluate the remaining ones) or that there need to be two
>>>>>> terminations - one that is 'soft' and won't allow ensure blocks to be
>>>>>> skipped and one that is 'hard' (kill -9 hard) and just ignores all the
>>>>>> ensure blocks.
>>>>>
>>>>> I'm only saying that normal usage (aka #terminate) shouldn't do
>>>>> unexpected
>>>>> things like this.
>>>>> If you read the comment of Process >> #terminate, you may assume that
>>>>> #ensure: and #ifCurtailed: blocks will be excuted even if you use
>>>>> #terminate, but that's not true.
>>>>>
>>>>> "Stop the process that the receiver represents forever.  Unwind to
>>>>> execute
>>>>> pending ensure:/ifCurtailed: blocks before terminating."
>>>>>
>>>>>
>>>>> Levente
>>>>>
>>>>
>>>> The only way I see to solve your problem would be to execute the
>>>> unwind block in another process...
>>>> Quite technical and costly !
>>>
>>> It's our problem. Just look at the senders of #ensure: and imagine what
>>> will
>>> happen if the termination block is not evaluated.
>>> I think there's another way (though it might be my lack of knowledge
>>> again).
>>> After suspending the process which is about to be terminated we can check
>>> if
>>> it's executing a termination block. It it's not, we are safe to continue
>>> the
>>> termination, otherwise we can do something else which ensures that the
>>> termination block is evaluated.
>>>
>>
>> Maybe...
>> Unfortunately, you did not tell how you will distinguish well behaved
>> unwind-blocks from Igor's example...
>
> I'd give the responsibility to the developer to write termination blocks
> which are safe to evaluate. So I assume that all such blocks behave well. If
> something goes wrong you can kill the process with a more aggressive
> method (as Andreas suggested), but you lose the guarantee that the current
> termination block will be evaluated.
>
>
> Levente
>

I would tend to focus first on the senders of terminate since
terminating is unsafe...
How many of them would deserve to be transformed in a terminateRequest ?

Nicolas

>>
>> Nicolas
>>
>>>
>>> Levente
>>>
>>>>
>>>> Nicolas
>>>>
>>>>>>
>>>>>> Cheers,
>>>>>>  - Andreas
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>>
>>>
>>
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