[langtools] RFR (L): 8010319: Implementation of JEP 181: Nest-Based Access Control

Tue May 15 08:13:41 UTC 2018

----- Mail original -----
> De: "Maurizio Cimadamore" <maurizio.cimadamore at oracle.com>
> À: "David Holmes" <david.holmes at oracle.com>, "compiler-dev" <compiler-dev at openjdk.java.net>
> Envoyé: Mardi 15 Mai 2018 09:59:43
> Objet: Re: [langtools] RFR (L): 8010319: Implementation of JEP 181: Nest-Based Access Control

> Hi David,
> the webrev looks good.
> 
> You did an excellent job in staying on top of all these different areas
> - kudos!

yes !

> 
> The only thing I can't decide is whether we will need an escape hatch
> flag for when you compile using -target 11 and, for some weird reason
> you need to disable nestmates (e.g. you want javac to emit accessors).
> But with all the testing you did, I'm confident that what we have is
> good - we can always add such a flag at a later stage - it's so trivial.

I agree with this strategy. Given that we are aligning the VM class semantics to the Java the language semantics, i do not think people will still want accessors, perhaps in a nightmare, 'i still want accessors otherwise the stacktraces are too easy to read', in 5 when ldc class was intoduced, nobody ask to keep the class accessor code.  

> 
> Cheers
> Maurizio

regards,
Rémi

> 
> 
> On 15/05/18 01:52, David Holmes wrote:
>> This review is being spread across four groups: langtools, core-libs,
>> hotspot and serviceability. This is the specific review thread for
>> langtools - webrev:
>>
>> http://cr.openjdk.java.net/~dholmes/8010319-JEP181/webrev.langtools.v1/
>>
>> See below for full details - including annotated full webrev guiding
>> the review.
>>
>> The intent is to have JEP-181 targeted and integrated by the end of
>> this month.
>>
>> Thanks,
>> David
>> -----
>>
>> The nestmates project (JEP-181) introduces new classfile attributes to
>> identify classes and interfaces in the same nest, so that the VM can
>> perform access control based on those attributes and so allow direct
>> private access between nestmates without requiring javac to generate
>> synthetic accessor methods. These access control changes also extend
>> to core reflection and the MethodHandle.Lookup contexts.
>>
>> Direct private calls between nestmates requires a more general calling
>> context than is permitted by invokespecial, and so the JVMS is updated
>> to allow, and javac updated to use, invokevirtual and invokeinterface
>> for private class and interface method calls respectively. These
>> changed semantics also extend to MethodHandle findXXX operations.
>>
>> At this time we are only concerned with static nest definitions, which
>> map to a top-level class/interface as the nest-host and all its nested
>> types as nest-members.
>>
>> Please see the JEP for further details.
>>
>> JEP: https://bugs.openjdk.java.net/browse/JDK-8046171
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8010319
>> CSR: https://bugs.openjdk.java.net/browse/JDK-8197445
>>
>> All of the specification changes have been previously been worked out
>> by the Valhalla Project Expert Group, and the implementation reviewed
>> by the various contributors and discussed on the valhalla-dev mailing
>> list.
>>
>> Acknowledgments and contributions: Alex Buckley, Maurizio Cimadamore,
>> Mandy Chung, Tobias Hartmann, Vladimir Ivanov, Karen Kinnear, Vladimir
>> Kozlov, John Rose, Dan Smith, Serguei Spitsyn, Kumar Srinivasan
>>
>> Master webrev of all changes:
>>
>> http://cr.openjdk.java.net/~dholmes/8010319-JEP181/webrev.full.v1/
>>
>> Annotated master webrev index:
>>
>> http://cr.openjdk.java.net/~dholmes/8010319-JEP181/jep181-webrev.html
>>
>> Performance: this is expected to be performance neutral in a general
>> sense. Benchmarking and performance runs are about to start.
>>
>> Testing Discussion:
>> ------------------
>>
>> The testing for nestmates can be broken into four main groups:
>>
>> -  New tests specifically related to nestmates and currently in the
>> runtime/Nestmates directory
>>
>> - New tests to complement existing tests by adding in testcases not
>> previously expressible.
>>   -  For example java/lang/invoke/SpecialInterfaceCall.java tests use
>> of invokespecial for private interface methods and performing receiver
>> typechecks, so we add java/lang/invoke/PrivateInterfaceCall.java to do
>> similar tests for invokeinterface.
>>
>> -  New JVM TI tests to verify the spec changes related to nest
>> attributes.
>>
>> -  Existing tests significantly affected by the nestmates changes,
>> primarily:
>>    -  runtime/SelectionResolution
>>
>>    In most cases the nestmate changes makes certain invocations that
>> were illegal, legal (e.g. not requiring invokespecial to invoke
>> private interface methods; allowing access to private members via
>> reflection/Methodhandles that were previously not allowed).
>>
>> - Existing tests incidentally affected by the nestmate changes
>>
>>   This includes tests of things utilising class
>> redefinition/retransformation to alter nested types but which
>> unintentionally alter nest relationships (which is not permitted).
>>
>> There are still a number of tests problem-listed with issues filed
>> against them to have them adapted to work with nestmates. Some of
>> these are intended to be addressed in the short-term, while some (such
>> as the runtime/SelectionResolution test changes) may not eventuate.
>>
>> - https://bugs.openjdk.java.net/browse/JDK-8203033
>> - https://bugs.openjdk.java.net/browse/JDK-8199450
>> - https://bugs.openjdk.java.net/browse/JDK-8196855
>> - https://bugs.openjdk.java.net/browse/JDK-8194857
>> - https://bugs.openjdk.java.net/browse/JDK-8187655
>>
>> There is also further test work still to be completed (the JNI and JDI
>> invocation tests):
>> - https://bugs.openjdk.java.net/browse/JDK-8191117
>> which will continue in parallel with the main RFR.
>>
>> Pre-integration Testing:
>>  - General:
>>     - Mach5: hs/jdk tier1,2
>>     - Mach5: hs-nightly (tiers 1 -3)
>>  - Targetted
>>    - nashorn (for asm changes)
>>    - hotspot: runtime/*
>>               serviceability/*
>>               compiler/*
>>               vmTestbase/*
>>    - jdk: java/lang/invoke/*
>>           java/lang/reflect/*
>>           java/lang/instrument/*
>>           java/lang/Class/*
>>           java/lang/management/*
>>   - langtools: tools/javac
>>                tools/javap