[Nestmates] RFR (S): 8197915: [Nestmates] Implement receiver typecheck for private invokeinterface use
David Holmes
david.holmes at oracle.com
Fri May 4 08:06:11 UTC 2018
On 4/05/2018 5:47 PM, Vladimir Ivanov wrote:
>
>>>>>> http://cr.openjdk.java.net/~dholmes/8197915/webrev.v2/
>>>>
>>>> src/java.base/share/classes/java/lang/invoke/DirectMethodHandle.java
>>>>
>>>> + LambdaForm lform = preparedLambdaForm(member,
>>>> callerClass.isInterface());
>>>>
>>>> You need to handle "callerClass == null" case as well.
>>>
>>> I'm not sure I do now. I think we must always have a callerClass
>>> context when we hit this code. Can you see where a null may come
>>> from? So far testing has not produced any failures relating to a null
>>> callerClass. If we did ever get a null we'd be missing the receiver
>>> <: caller check, and that would be a bug requiring us to change the
>>> code to pass in the caller.
>>
>> Just realized this is inconsistent with the immediately following:
>>
>> if (callerClass != null) {
>> checkClass = callerClass; // potentially strengthen to caller class
>> }
>
> Yes, that's what initially draw my attention.
>
>>
>> So I'll have to change one of them. But I'd still prefer that the
>> callerClass can not be null.
>
> I agree with you that DMH.make() should not observe both
> m.getReferenceKind() == REF_invokeSpecial and callerClass == null at the
> same time.
>
> If you want to rely on "callerClass != null" for now, then add an
> explicit check and throw InternalError instead of NPE.
Ok. webrev updated to v3:
http://cr.openjdk.java.net/~dholmes/8197915/webrev.v3/
New code:
// if caller is an interface we need to adapt to get the
// receiver check inserted
if (callerClass == null) {
throw new InternalError("callerClass must not be null for
REF_invokeSpecial");
}
LambdaForm lform = preparedLambdaForm(member,
callerClass.isInterface());
return new Special(mtype, lform, member, callerClass);
Thanks,
David
> Best regards,
> Vladimir Ivanov
>
>>>>>>
>>>>>> Changes:
>>>>>>
>>>>>> - DirectMethodHandles.java: new simple and direct approach to
>>>>>> dealing with LF_SPECIAL_IFC
>>>>>
>>>>> I like how java.lang.invoke part shapes out!
>>>>>
>>>>> Maybe rename adaptToSpecialIfc to needsReceiverCheck? That's what
>>>>> confused me in the first version: though it's an interface call
>>>>> (which always require receiver check against REFC), new checks only
>>>>> referred to LF_INVSPECIAL (since invocation mode is a direct call).
>>>>>
>>>>>> - New regression test for the final virtual call from an interface
>>>>>> bug introduced by 8200167.
>>>>>>
>>>>>> If necessary/desirable I can fix that part in mainline separately.
>>>>>> So far no tests (including jck/API/java/lang) seem to tickle it.
>>>>>
>>>>> Or file a bug. I have some ideas how to improve relevant code and
>>>>> make LF construction cleaner.
>>>>>
>>>>> Best regards,
>>>>> Vladimir Ivanov
>>>>>
>>>>>
>>>>>> Thanks,
>>>>>> David
>>>>>>
>>>>>> On 4/05/2018 11:41 AM, David Holmes wrote:
>>>>>>> Hi Karen,
>>>>>>>
>>>>>>> On 4/05/2018 6:39 AM, Karen Kinnear wrote:
>>>>>>>> David,
>>>>>>>>
>>>>>>>> Really delighted to see you near the end of the major functional
>>>>>>>> changes!
>>>>>>>
>>>>>>> Thanks for taking a look so quickly!
>>>>>>>
>>>>>>>> A couple minor comments, and then a question please:
>>>>>>>>
>>>>>>>> 1. MethodHandles.java
>>>>>>>
>>>>>>> DirectMethodHandle.java :)
>>>>>>>
>>>>>>>> 174 different “to” -> different “from” ?
>>>>>>>
>>>>>>> Changed. That's my UK upbringing :)
>>>>>>>
>>>>>>> https://en.oxforddictionaries.com/usage/different-from-than-or-to
>>>>>>>
>>>>>>>> 2. methodHandles.cpp
>>>>>>>> 300-301
>>>>>>>> Thank you for the comment.
>>>>>>>> Might it also be worth adding that direct call is used by:
>>>>>>>> invoke static, invokespecial, invokeinterface:local
>>>>>>>> private, invoke virtual:vfinal and private methods
>>>>>>>> (or are you concerned about getting out of sync if this
>>>>>>>> changes?)
>>>>>>>
>>>>>>> It is not used by invokestatic. I'm not 100% sure of all the
>>>>>>> exact cases where an invokeinterface/invokevirtual becomes a
>>>>>>> direct call, so didn't want to say anything inaccurate. But the
>>>>>>> comment as it stands is awkward so I've expanded it:
>>>>>>>
>>>>>>> // "special" reflects that this is a direct call, not that it
>>>>>>> // necessarily originates from an invokespecial. We can
>>>>>>> also do
>>>>>>> // direct calls for private and/or final non-static methods.
>>>>>>>
>>>>>>>> 3. DirectMethodHandle.java - this was subtle!
>>>>>>>
>>>>>>> More than you realise ;-)
>>>>>>>
>>>>>>>> I believe this is correct assuming that:
>>>>>>>> CallerClass is always and only set for invokespecial. Is this
>>>>>>>> accurate? Could you possibly add a comment?
>>>>>>>
>>>>>>> That's an excellent question and one that should have been asked
>>>>>>> before 8200167 was finalized. :( The short answer is "no" -
>>>>>>> callerClass can be non-null for any of the invocation modes. And
>>>>>>> yes the current mainline code is broken - seems there is a gap in
>>>>>>> the existing test coverage as we never call a final method from
>>>>>>> an interface method. If we do we get:
>>>>>>>
>>>>>>> Exception in thread "main" java.lang.InternalError: Should only
>>>>>>> be invoked on a subclass
>>>>>>> at
>>>>>>> java.base/java.lang.invoke.DirectMethodHandle.checkReceiver(DirectMethodHandle.java:441)
>>>>>>>
>>>>>>>
>>>>>>> <sigh>
>>>>>>>
>>>>>>> We only look at callerClass when dealing with LF_INVSPECIAL,
>>>>>>> which in mainline means we either have an invokespecial or an
>>>>>>> invokevirtual. For invokespecial this is fine of course. But the
>>>>>>> invokevirtual case was never encountered and so slipped by in
>>>>>>> error. With nestmates we also add invokeinterface to the mix -
>>>>>>> which is fine because if it is an invokeinterface then we want
>>>>>>> the check regardless. It doesn't matter if the check is enabled
>>>>>>> because of the (incidental) callerClass.isInterface check, or the
>>>>>>> explicit m.getDeclaringClass().isInterface(). But the logic is
>>>>>>> messy and far from clear and not correct by construction. So I
>>>>>>> will completely redo it in a simpler and more direct/explicit way.
>>>>>>>
>>>>>>> BTW another red-herring: the !m.isStatic() part of the condition
>>>>>>> was not needed. I was tracking down two failure modes before
>>>>>>> finalizing this. The first was a problem with a static interface
>>>>>>> method - fixed by the !m.isStatic(). The second was caused by
>>>>>>> missing parentheses in the overall condition - which once fixed
>>>>>>> precluded the static case, so the first fix was not needed (as we
>>>>>>> never use LF_INVSPECIAL with statics). If only I'd tackled them
>>>>>>> in the reverse order.
>>>>>>>
>>>>>>> I'll post an updated webrev later today once I've re-tested lots
>>>>>>> of things.
>>>>>>>
>>>>>>>> - agree with the theory that invokevirtual will never find a
>>>>>>>> private interface method (and ACC_FINAL is illegal for interfaces)
>>>>>>>
>>>>>>> Yes. More specifically as we're dealing with MH semantics:
>>>>>>> findVirtual for an interface method yields a MH with
>>>>>>> invokeInterface "kind", not one with invokeVirtual "kind".
>>>>>>>
>>>>>>> public MethodHandle findVirtual(Class<?> refc, String name,
>>>>>>> MethodType type) throws NoSuchMethodException,
>>>>>>> IllegalAccessException {
>>>>>>> ...
>>>>>>> byte refKind = (refc.isInterface() ? REF_invokeInterface :
>>>>>>> REF_invokeVirtual);
>>>>>>> ...
>>>>>>> }
>>>>>>>
>>>>>>>
>>>>>>>> 4. Test - I still need to study this
>>>>>>>> I have been writing down test cases to make sure we don’t test
>>>>>>>> cases we don’t want to, and I
>>>>>>>> need to double-check you have them covered. Will do that tomorrow.
>>>>>>>
>>>>>>> The testing is all "positive" in the sense that it ensures a
>>>>>>> receiver subtype check is in place when it "must be". In fact it
>>>>>>> must always be the case the receiver has a type that has the
>>>>>>> method being invoked. We were just missing a few cases that
>>>>>>> verified that (and some stronger conditions: ie receiver <:
>>>>>>> caller for invokespecial semantics).
>>>>>>>
>>>>>>> If you want to test that we don't insert the new explicit checks
>>>>>>> in cases where they are not needed, then I don't know how to do
>>>>>>> that - other than by adding tracing and running the test case and
>>>>>>> not seeing checkReceiver being called.
>>>>>>>
>>>>>>> That said, once I've reworked the logic it will be blindingly
>>>>>>> obvious when the new explicit check is being added.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> David
>>>>>>>
>>>>>>>
>>>>>>>> thanks,
>>>>>>>> Karen
>>>>>>>>
>>>>>>>>> On May 3, 2018, at 6:21 AM, David Holmes
>>>>>>>>> <david.holmes at oracle.com> wrote:
>>>>>>>>>
>>>>>>>>> bug id: https://bugs.openjdk.java.net/browse/JDK-8197915
>>>>>>>>> webrev: http://cr.openjdk.java.net/~dholmes/8197915/webrev/
>>>>>>>>>
>>>>>>>>> JDK-8174962 implemented receiver typechecks for invokeinterface
>>>>>>>>> within the interpreter (templateTable), compilers and for
>>>>>>>>> MethodHandles. In nestmates invokeinterface can now be used for
>>>>>>>>> private interface methods - which result in direct calls. So we
>>>>>>>>> need to extend the receiver subtype checks to cover the new cases.
>>>>>>>>>
>>>>>>>>> Summary of changes:
>>>>>>>>>
>>>>>>>>> - src/hotspot/cpu/<cpu>/templateTable_<cpu>.cpp
>>>>>>>>>
>>>>>>>>> In the templateTable the 8174962 checks come after the private
>>>>>>>>> interface method invocation logic ("vfinal") we already had in
>>>>>>>>> place for the nestmate changes, and they rely on itable
>>>>>>>>> information that doesn't exist for private methods. So we
>>>>>>>>> insert a direct subtype check.
>>>>>>>>>
>>>>>>>>> I've provided code for all CPU's but only x86 and sparc have
>>>>>>>>> been tested. I'll be soliciting aid on the other ports before
>>>>>>>>> nestmates goes to mainline later this month.
>>>>>>>>>
>>>>>>>>> - src/hotspot/share/oops/cpCache.cpp
>>>>>>>>>
>>>>>>>>> We have to pass the interface klass* so it's available for the
>>>>>>>>> typecheck.
>>>>>>>>>
>>>>>>>>> - src/hotspot/share/oops/klassVtable.cpp
>>>>>>>>>
>>>>>>>>> Updated a comment that's no longer accurate.
>>>>>>>>>
>>>>>>>>> - src/hotspot/share/opto/doCall.cpp
>>>>>>>>>
>>>>>>>>> This code was provided by Vladimir Ivanov (thank you!) and
>>>>>>>>> expands the existing "invokespecial" support for receiver
>>>>>>>>> typechecks in C2, to "invokeinterface" as well.
>>>>>>>>>
>>>>>>>>> Aside: no changes were needed for C1. It's seems all the
>>>>>>>>> receiver typechecks for C1 are being handled at a higher level
>>>>>>>>> (through linkResolver and/or cpCache logic).
>>>>>>>>>
>>>>>>>>> - src/hotspot/share/prims/methodHandles.cpp
>>>>>>>>>
>>>>>>>>> Comment clarifying JVM_REF_invokeSpecial doesn't necessarily
>>>>>>>>> mean it relates to an actual "invokespecial" - it is used for
>>>>>>>>> all direct calls.
>>>>>>>>>
>>>>>>>>> -
>>>>>>>>> src/java.base/share/classes/java/lang/invoke/DirectMethodHandle.java
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Add clarifying comments regarding how "kind" can vary if a
>>>>>>>>> direct call is involved.
>>>>>>>>>
>>>>>>>>> Expand the condition to switch from LF_INVSPECIAL to
>>>>>>>>> LF_INVSPECIAL_IFC (which adds the additional receiver
>>>>>>>>> typecheck) to account for the invokeinterface case.
>>>>>>>>>
>>>>>>>>> - test/jdk/java/lang/invoke/PrivateInterfaceCall.java
>>>>>>>>>
>>>>>>>>> New test for invokeinterface semantics that mirrors the
>>>>>>>>> existing SpecialInterfaceCall test for invokespecial.
>>>>>>>>>
>>>>>>>>> This is the last of the significant functional changes for
>>>>>>>>> nestmates.
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> David
>>>>>>>>
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