Reachability of an object when a thread is running one of its methods

[Carlo de Wolf]

On 12/04/2012 08:41 PM, Andrew Haley wrote:
> On 12/04/2012 06:35 PM, Carlo de Wolf wrote:
>> On 12/04/2012 05:05 PM, Andrew Haley wrote:
>>> On 12/04/2012 12:12 PM, Carlo de Wolf wrote:
>>>> JLS 7 12.6.1:
>>>> Note that this sort of optimization is only allowed if references are on
>>>> the stack, not stored in
>>>> the heap.
>>>>
>>>> This hints to me that an object which is on the stack (of the previous
>>>> frame) is actually strong referenced.
>>> What is your reason for believing that references in previous frames
>>> are any stronger than references in the current frame?  I can't see
>>> anything that implies it.
>>>
>> I don't believe that. But it's a reference on the stack of the previous
>> frame, while a local variable reference on the current frame.
> OK, but you said:
>
>>>> This hints to me that an object which is on the stack (of the previous
>>>> frame) is actually strong referenced.
> which is what I don't understand.  Why do you think there is such a hint?
> I can't see any such hint in what you quoted.
>
> Andrew.
>
The example further on shows that an object reference which is on the 
heap can be optimized away and thus the object can be finalized too 
early. A reference coming off the stack is allowed to be nullified and 
it would not trigger finalization. Hence a reference on the stack is a 
strong one.
Probably the real issue is when the stack of the previous frame is 
cleared, at the start of invoke(virtual) or at the end of invoke(virtual)?

Carlo