On 2/01/2018 6:21 PM, Langer, Christoph wrote:
Hi David,
thanks for pointing this out. I see what you mean.
However, you were the one who brought up the point that rather the Location interface should specify the means to compare two Locations :)
All I meant by that is that Location should _specify_ what it means to
compare two Locations. Any interface (or class for that matter) that
implements Comparable should provide an overriding specification for
compareTo.
And that would be an interface default method - or would there be another way?
I guess, as there are no generics involved, the overloading instead of
overriding thing should at least be more obvious for other implementers of the
Location interface. But, for sure, I'm leaving the decision whether the default
interface is the right thing here or not to better language and jdi experts
than I am. Egor's original proposal should work well, too, and is definitely
less obtrusive.
Yeah I'm going to punt on this one too. :)
BTW: your suggested change in MirrorImpl to go from "protected VirtualMachineImpl vm;" to
"protected VirtualMachine vm;" would not really work out as VirtualMachineImpl extends
MirrorImpl and in there VirtualMachineImpl is definitely needed. It's really a bit weird...
Thanks for checking. Despite the use of interfaces and classes this
stuff doesn't really seem to be that amenable to supporting alternative
implementations of the interfaces.
Cheers,
David
Best regards
Christoph
-----Original Message-----
From: David Holmes [mailto:david.hol...@oracle.com]
Sent: Dienstag, 2. Januar 2018 08:31
To: Langer, Christoph <christoph.lan...@sap.com>; Egor Ushakov
<egor.usha...@jetbrains.com>; serguei.spit...@oracle.com;
serviceability-dev@openjdk.java.net
Subject: Re: RFR: cleanup - removed unneeded casts in jdi
Hi Christoph,
On 2/01/2018 4:41 PM, Langer, Christoph wrote:
Hi Egor, David and Serguei,
I had a look at this, too. I would think this really calls out for a
“public default int compareTo(Location other) {…}” in Location.java
I think this could run into the "overloads instead of overrides" problem
that Brian describes here:
http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-November/050060.html
... unsure. But this would need a CSR request any way so hopefully any
issues with doing this would be caught there.
I'm very wary of adding default methods, though this may be such a
little used interface that it's not really an issue.
Cheers,
David
which uses the implementation out of LocationImpl.java. That way, all
the suggested improvements for MirrorImpl.java can be done as well. And
other implementers of Location, such as IntelliJ’s
GeneratedLocation.java, would still build and won’t be necessarily wrong
but could probably gradually remove their compareTo methods.
As for checking for the same VM within Location comparison, e.g. by
using the equals() method, I guess this can be added. At least it should
not add a notable cost. But I suggest to do it with a separate change,
in case it turns out to be not a good idea and one needs to revert it.
@Egor: Would you mind to create an updated Webrev with an interface
default method?
Best regards
Christoph
*From:*serviceability-dev
[mailto:serviceability-dev-boun...@openjdk.java.net] *On Behalf Of *Egor
Ushakov
*Sent:* Montag, 25. Dezember 2017 12:30
*To:* serguei.spit...@oracle.com; David Holmes
<david.hol...@oracle.com>; serviceability-dev@openjdk.java.net
*Subject:* Re: RFR: cleanup - removed unneeded casts in jdi
Thanks for your comments!
I'll try to provide more details:
We have our own Location implementaion in IDEA code:
GeneratedLocation.java
<https://github.com/JetBrains/intellij-community/blob/29cdd102746d2252ef282082e7671128228489f8/java/debugger/impl/src/com/intellij/debugger/jdi/GeneratedLocation.java>
which is not intended to be used inside the jdi, but mostly to mock
Location in our own APIs like PositionManager.java
<https://github.com/JetBrains/intellij-community/blob/306d705e1829bd3c74afc2489bfb7ed59d686b84/java/debugger/openapi/src/com/intellij/debugger/PositionManager.java>
Unfortunately some implementations keep the provided Location objects
(both LocationImpl and ours) in collections (maybe sorted) so we have to
prevent cast exceptions from compareTo somehow.
Hope it helps.
Egor
On 24-Dec-17 03:32, serguei.spit...@oracle.com
<mailto:serguei.spit...@oracle.com> wrote:
Hi David,
Thank you for the explanations!
I've got your points.
On 12/23/17 15:32, David Holmes wrote:
Hi Serguei,
On 23/12/2017 6:04 PM, serguei.spit...@oracle.com
<mailto:serguei.spit...@oracle.com> wrote:
Hi Egor and David,
Egor,
The fix looks good in general.
I've filed bug:
https://bugs.openjdk.java.net/browse/JDK-8194143
remove unneeded casts in LocationImpl and MirrorImpl
classes
On 12/22/17 13:06, David Holmes wrote:
Hi Egor,
On 23/12/2017 1:32 AM, Egor Ushakov wrote:
Hi all,
could you please review and sponsor this small
cleanup removing unneeded casts in jdi LocationImpl
and MirrorImpl.
They were preventing creating custom Location and
Mirror implementations used for tests and IDEA
debugger impl.
http://cr.openjdk.java.net/~avu/egor.ushakov/cast_fix/
src/jdk.jdi/share/classes/com/sun/tools/jdi/LocationImpl.java
! public int compareTo(Location object) {
- LocationImpl other = (LocationImpl)object;
The existing code is somewhat suspect as the Location
interface implements Comparable but it does not specify
what it means to compare two Locations! That's a bug in
itself.
Not sure, if it is really needed as it is abstract.
We could say: An implementation of the Location is expected
to specify it.
That makes it impossible to compare different implementations of
the Location interface. The functionality has to be specified by
the interface.
We probably never needed to compare them before.
But such comparison can be needed for an IDE that has a deal with
different JDI implementations.
LocationImpl has decided how to compare two
LocaltionImp's (but doesn't even check they are in the
same VirtualMachine!).
Nice catch!
Interesting...
Should comparing of locations from different mirrors be a
no-op?
Not sure if it would be right to throw a VMMismatchException
in such cases.
Not sure - without knowing why we need to compare Locations it's
hard to say.
Ok.
Can we generalize that to accommodate other Location
implementations?Your change allows for this to happen,
but it will only work as expected if the other Location
implementations use the same comparison basis as
LocationImpl - which is unspecified.
It is not clear, what you mean here.
What are the other Location implementations?
The ones that Egor is implementing and the reason for this bug
report.
It is not clear to me why do they need their own Location
implementation.
A JDI implementation normally has one base implementation of
the Location.
What would be a need to have multiple?
Egor indicated it was for use in testing and the IDEA debugger.
It's apparent they have their own implementation of Location,
but these instances have to interact with the default
LocationImpl implementations - else this bug report would not be
needed.
Will need to look at it more closely after NY.
I'm going to vacation in a couple of hours until the Jan 3-rd.
Will probably have a limited internet access there.
I wish you, guys, happy Xmas and New Year and nice Holidays!
Thanks,
Serguei
Cheers,
David
And different JDI implementations are not supposed to
interact with each other, are they?
src/jdk.jdi/share/classes/com/sun/tools/jdi/MirrorImpl.java
Change looks good. It would also seem that now this
change is made that this:
37 protected VirtualMachineImpl vm;
38
39 MirrorImpl(VirtualMachine aVm) {
40 super();
41
42 // Yes, its a bit of a hack. But by doing
it this
43 // way, this is the only place we have to
change
44 // typing to substitute a new impl.
45 vm = (VirtualMachineImpl)aVm;
might reduce to:
37 protected VirtualMachine vm;
38
39 MirrorImpl(VirtualMachine aVm) {
40 super();
41 vm = aVm;
if we no longer depend on it being VirtualMachineImpl
... and neither do subclasses.
Good suggestion.
Thanks,
Serguei
David
-----
I do not have rights to create JDK bug report
directly, please create it if it is needed for the
procedure.
Thanks!
--
Egor Ushakov
Software Developer
JetBrains
http://www.jetbrains.com
The Drive to Develop
