[9] RFR (S): 8036117: MethodHandles.catchException doesn't handle VarargsCollector right (8034120 failed)

[Peter Levart]

Hi,

Excuse my ignorant question: What is the purpose of @LambdaForm.Hidden 
annotation?

I suspect it has to do with hiding the call frames in stack traces that 
are part of LambdaForm invocation chain. In this case, method:

	private static Object[] prepend(Object elem, Object[] array)

in MethodHandleImpl need not be annotated with this annotation, since 
it's call frame is not on stack when one of the target methods is 
executed. It's just a function used to calculate the argument of the 
call. In fact, if prepend() ever throws exception (NPE in case array is 
null?), It would be preferable that it's call frame is visible in the 
stack trace.

Am I right or am I just talking nonsense?

Regards, Peter


On 03/11/2014 12:12 AM, Vladimir Ivanov wrote:
> John, Chris, thanks!
>
> Best regards,
> Vladimir Ivanov
>
> On 3/11/14 3:08 AM, Christian Thalinger wrote:
>> Even better.
>>
>> On Mar 10, 2014, at 3:21 PM, Vladimir Ivanov 
>> <vladimir.x.ivanov at oracle.com> wrote:
>>
>>> Chris, thanks for the review.
>>>
>>> John suggested an elegant way to fix the problem - use asFixedArity.
>>>
>>> Updated fix:
>>> http://cr.openjdk.java.net/~vlivanov/8036117/webrev.01/
>>>
>>> Best regards,
>>> Vladimir Ivanov
>>>
>>> On 3/8/14 4:51 AM, Christian Thalinger wrote:
>>>> Seems good to me.  I’d like to have another name for this method:
>>>>
>>>> +     private static Object invokeCustom(MethodHandle target, 
>>>> Object... args) throws Throwable {
>>>>
>>>> On Mar 4, 2014, at 12:00 PM, Vladimir Ivanov 
>>>> <vladimir.x.ivanov at oracle.com> wrote:
>>>>
>>>>> http://cr.openjdk.java.net/~vlivanov/8036117/webrev.00/
>>>>> https://bugs.openjdk.java.net/browse/JDK-8036117
>>>>> 84 lines changed: 74 ins; 3 del; 7 mod
>>>>>
>>>>> I have to revert a cleanup I did for 8027827.
>>>>> MethodHandle.invokeWithArguments (and generic invocation) has 
>>>>> unpleasant
>>>>> peculiarity in behavior when used with VarargsCollector. So,
>>>>> unfortunately, invokeWithArguments is not an option there.
>>>>>
>>>>> Looking at the API (excerpts from javadoc [1] [2]), the following
>>>>> condition doesn't hold in that case:
>>>>>    "trailing parameter type of the caller is a reference type 
>>>>> identical
>>>>> to or assignable to the trailing parameter type of the adapter".
>>>>>
>>>>> Example:
>>>>>    target.invokeWithArguments((Object[])args)
>>>>>    =>
>>>>>    target.invoke((Object)o1,(Object)o2,(Object)o3)
>>>>>    =/>
>>>>>    target.invokeExact((Object)o1, (Object)o2, (Object[])o3)
>>>>>
>>>>> because Object !<: Object[].
>>>>>
>>>>> The fix is to skip unnecessary conversion when invoking a method 
>>>>> handle
>>>>> and just do a pairwise type conversion.
>>>>>
>>>>> Testing: failing test case, nashorn w/ experimental features (octane)
>>>>>
>>>>> Thanks!
>>>>>
>>>>> Best regards,
>>>>> Vladimir Ivanov
>>>>>
>>>>> [1] MethodHandle.invokeWithArguments
>>>>> "Performs a variable arity invocation, ..., as if via an inexact 
>>>>> invoke
>>>>> from a call site which mentions only the type Object, and whose 
>>>>> arity is
>>>>> the length of the argument array."
>>>>>
>>>>> [2] MethodHandle.asVarargsCollector
>>>>> "When called with plain, inexact invoke, if the caller type is the 
>>>>> same
>>>>> as the adapter, the adapter invokes the target as with invokeExact.
>>>>> (This is the normal behavior for invoke when types match.)
>>>>>
>>>>> Otherwise, if the caller and adapter arity are the same, and the
>>>>> trailing parameter type of the caller is a reference type 
>>>>> identical to
>>>>> or assignable to the trailing parameter type of the adapter, the
>>>>> arguments and return values are converted pairwise, as if by 
>>>>> asType on a
>>>>> fixed arity method handle.
>>>>>
>>>>> Otherwise, the arities differ, or the adapter's trailing parameter 
>>>>> type
>>>>> is not assignable from the corresponding caller type. In this 
>>>>> case, the
>>>>> adapter replaces all trailing arguments from the original trailing
>>>>> argument position onward, by a new array of type arrayType, whose
>>>>> elements comprise (in order) the replaced arguments."
>>>>> _______________________________________________
>>>>> mlvm-dev mailing list
>>>>> mlvm-dev at openjdk.java.net
>>>>> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
>>>>
>>>> _______________________________________________
>>>> mlvm-dev mailing list
>>>> mlvm-dev at openjdk.java.net
>>>> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
>>>>
>>> _______________________________________________
>>> mlvm-dev mailing list
>>> mlvm-dev at openjdk.java.net
>>> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
>>
>> _______________________________________________
>> mlvm-dev mailing list
>> mlvm-dev at openjdk.java.net
>> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
>>
> _______________________________________________
> mlvm-dev mailing list
> mlvm-dev at openjdk.java.net
> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev