Hi Mandy,
On 11/16/2016 07:11 AM, Mandy Chung wrote:
On Nov 15, 2016, at 4:41 AM, Zoltán Majó <zoltan.m...@oracle.com> wrote:
I think the sentence in webrev.01
(1) "If a registered referenceceases to be strongly reachable itself, then it may
never be enqueued."
is sufficient. I think we want to make a statement only about what happens when
a reference ceases to be strongly reachable (i.e., that in that case we can't
make a statement about that reference being enqueued or not).
When a reference becomes unreachable (not by examining the source code but the
actual state of the VM at runtime), it will never be enqueued.
I also like that wording, thank you!
The sentence you suggested
(2) "A Java virtual machine may implement optimization that could affects when
objects become unreachable."
adds too much ambiguity as it leaves room for speculation about what
"optimization" might be.
For example, statement (2) can be possibly (mis-)read as the JVM making
references unreachable *earlier* than what a programmer may think -- based on
the source code.(That is clearly not the case: References are available at
least until the latest program point where they are used, otherwise the program
would encounter an error.)
It's indeed a JVM "optimization" keep references alive *longer* than it seems
to be from the source code. But (1) already encapsulates that without referring to JVM
optimizations explicitly.
That’s fair.
What I’m looking for is something like this [1]:
Reachability is not determined by the statements in your source code but by the
actual state of the virtual machine at runtime.
OK, I see now -- thank you for explaining.
Here is a new webrev (webrev.03) that includes what you suggested:
http://cr.openjdk.java.net/~zmajo/8169000/webrev.03/
We could go either with this webrev or with the previous one (webrev.02)
that changes "will never be enqueued" to "may never be enqueued".
http://cr.openjdk.java.net/~zmajo/8169000/webrev.02/
I'm not sure which webrev is the better option.
Thank you!
Best regards,
Zoltan
Mandy
[1] The Java Programming Language, Fourth Edition, section 17.5.4
