Bug in MethodHandles.convertArguments

[Raffaello Giulietti]

On 2010-05-11 12:27, Rémi Forax wrote:
> Le 11/05/2010 09:31, Raffaello Giulietti a écrit :
>> Yes, this seems a bug to me, too.
>>
>> What about converting to Integer.class instead of int.class and letting
>> the boxing duties to the language compiler?
>>
>> Raffaello
>>    


Mmmm, I see.

However, filterArguments might not combine well with tail calls. So,
let's hope that convertArguments will work as expected asap. Did you
find out if it's indeed a bug?



> 
> This code is extracted from a bigger code that try to avoid boxing
> if not necessary.
> 
> echo a + 3
> is compiled:
> aload (a)
> iconst_3
> invokedynamic plus(Object,int)Object
> 
> and at runtime if 'a' contains an Integer, I install a fast path
> that checks if 'a' is an Integer and calls int+int.
> So the fast path doesn't need to box '3'.
> The slow path, box the int and call a method that will modify
> the fast path.
> 
> I am currently not a able to call that method because converting
> an int to an object doesn't work.
> 
> I see two workarounds:
> - have one slow path by signatures:
>    (int,Object), (double, Object), (Object, int) (Object, double), etc.
> - don't rely on convert and use filterArguments.
> 
> 
> Rémi
> 
>>
>> On 2010-05-10 21:11, Rémi Forax wrote:
>>    
>>> For me it's a new bug.
>>> I have checked with jdk7 latest binaries
>>> I will check with the mlvm repository sources when I will be at my
>>> office with a fast connection.
>>>
>>> public class ConvertBug {
>>>     public static Object foo(Object o1, Object o2) {
>>>       return null;
>>>     }
>>>
>>>     public static void main(String[] args) {
>>>       MethodHandle mh =
>>> MethodHandles.lookup().findStatic(ConvertBug.class, "foo",
>>>           MethodType.methodType( Object.class, Object.class, Object.class));
>>>       mh = MethodHandles.convertArguments(mh,
>>>           MethodType.methodType(Object.class, int.class, Object.class));
>>>       System.out.println("print mh "+mh);
>>>     }
>>> }
>>>
>>> Exception in thread "main" java.lang.IllegalArgumentException:
>>> mismatched parameter count
>>>       at sun.dyn.MemberName.newIllegalArgumentException(MemberName.java:409)
>>>       at sun.dyn.MethodHandleImpl.convertArguments(MethodHandleImpl.java:654)
>>>       at sun.dyn.ToGeneric.<init>(ToGeneric.java:102)
>>>       at sun.dyn.ToGeneric.of(ToGeneric.java:257)
>>>       at sun.dyn.ToGeneric.make(ToGeneric.java:249)
>>>       at sun.dyn.MethodHandleImpl.convertArguments(MethodHandleImpl.java:671)
>>>       at java.dyn.MethodHandles.convertArguments(MethodHandles.java:811)
>>>       at ConvertBug.main(ConvertBug.java:15)
>>>
>>>
>>> and I don't see any workaround :(
>>>
>>> Rémi
>>> _______________________________________________
>>> mlvm-dev mailing list
>>> mlvm-dev at openjdk.java.net
>>> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
>>>      
>> _______________________________________________
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>>    
> 
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