[squeak-dev] Re: [Pharo-project] #ensure: issues

Bert Freudenberg bert at freudenbergs.de
Thu Mar 4 21:09:49 UTC 2010

On 04.03.2010, at 21:57, Levente Uzonyi wrote:
> On Thu, 4 Mar 2010, Igor Stasenko wrote:
>> 2010/3/4 Levente Uzonyi <leves at elte.hu>:
>>> Here's a simple example (replace file with any external resource):
>>> My process opened a file, a termination block will close it if it's
>>> evaluated. If I send #terminate to the process I expect my file to be
>>> closed, so I won't leak a file descriptor.
>>> If the file can't be closed (aka the termination block raised an error) then
>>> there's a serious problem. It doesn't really matter what happens then.
>>> But I don't have to try to convince you anymore, because Andreas is about to
>>> solve the issue.
>> I'm not trying to convince anyone, i just wanted to show you that
>> there is no good solution in that plane.
>> More workarounds means more code to run (and makes things more complex, btw).
>> But you will be still unsafe.You will be safe, once you stop relying
>> on #ensure: in your code and use different approach.
>> As for your example: use weak finalizer to close your file.
> I'm about to get rid of the weak finalizer in cases where we know the exact scope when a file is used (as with #*FileNamed:do:). There's no point in registering and unregistering a file to the WeakRegistry if #ensure: closes the file for us at the right time.
>> This will make sure that no matter what were happen, you wont leave
>> the file open. Working with external resources is a pain. But lets try
>> to not poison ourselves with manual resource management, which comes
>> from C world.
> That's exactly what I'm about to do, keeping the resource management automatic (from the user POV) while making it fast.
> You can read my monologue about these plans here: http://lists.squeakfoundation.org/pipermail/squeak-dev/2010-February/144993.html
> Levente

Well, the finalizers are a safety net for file handles only anyway. Developers are advised to close files asap, and any code I have seen at least tries to do that. Why would you want to remove those finalizers?

- Bert -

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