Archie Cobbs wrote:
> Tim Ellison wrote:
>
>>>>> Off tanget, but IMHO this is not strictly true: it depends on whether
>>>>> VM native code relies on finalize() to free up its (non-heap) memory.
>>>>> Here's an exmaple of this:
>>>>>
>>>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4797189
>>>>
>>>>
>>>> That problem doesn't occur with GNU Classpath since our zip
>>>> implementation is written in java itself. But we have a similar example
>>>> in the mauve testsuite (one that I also observed while getting JBoss to
>>>> work with GNU Classpath and JamVM). There is a test that opens lots of
>>>> FileInputStreams and then expects the garbage collector to finalize
>>>> these and free up the open file descriptors. gcj explicitly handles
>>>> this
>>>> by forcing a garbage collect and finalization pass when it cannot
>>>> create
>>>> a new file descriptor. We currently don't have any convention for
>>>> marking VMObjects or finalizers as (scarce) holding native resources or
>>>> make the native code signal the runtime to do a finalization of such
>>>> objects.
>>>
>>>
>>> Right, and so this is a bug (although in a different form than
>>> the ZIP example above) in Classpath too. It could be fixed
>>
>>
>> I think it is unfair to describe this as 'a bug'. The FileInputStream
>> has a lifecycle (from open() to close()) that users are expected to
>> follow. While in this case you could image a VM knowing about the file
>> handle resources and trying to free them using finalization, such a fix
>> only inches you towards a fuller automatic resource management. There
>> are still many other areas (SQL cursors, window handles, etc.) that have
>> to be explicitly managed by the application.
>
>
> Right.. so the question boils down to this: should an application's
> unreferencing some object be considered as good as close()ing it (or
> hatever) with respect to this lifecycle? Guess that's open to debate.
> It's not clear that it actually can be even if you wanted it to.
Agreed, finalization is not a substitute for an explicit disposal.
> At least, the behavior should be documented with the class, as
> it's a pretty subtle point.
Sure. The wikipedia entry on finalization does a prety good job of
explaining the point:
http://en.wikipedia.org/wiki/Finalizer
Regards,
Tim
> -Archie
>
> __________________________________________________________________________
> Archie Cobbs * CTO, Awarix * http://www.awarix.com
>
--
Tim Ellison ([EMAIL PROTECTED])
IBM Java technology centre, UK.
