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

[John Rose]

Reviewed. 

– John

> 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