Re: How to modify instructions in BootstrapMethods using ASM?

It appears to work so far.

-David

On Thu, Nov 30, 2017 at 12:23 PM, <[email protected]> wrote:

>
>
> ------------------------------
>
> *De: *"David Dunkle" <[email protected]>
> *À: *"Remi Forax" <[email protected]>
> *Cc: *"asm" <[email protected]>
> *Envoyé: *Jeudi 30 Novembre 2017 20:53:51
> *Objet: *Re: [asm] How to modify instructions in BootstrapMethods using
> ASM?
>
> I got an interesting answer on stack overflow:
> https://stackoverflow.com/questions/47561756/how-to-
> modify-instructions-in-java-bootstrapmethods-using-asm
>
> Perhaps that answer is a more verbose statement of the same thing Remi has
> been telling me?
>
>
> yes, this mysterious Holger is better at explaining things than me :)
>
>
> -David
>
>
> Rémi
>
>
> On Thu, Nov 30, 2017 at 7:09 AM, David Dunkle <[email protected]>
> wrote:
>
>> I am doing that now,  but I don’t see how changing the reference to the
>> bootstrap method allows me to change the instructions of the existing
>> bootstrap methods.
>>
>> Am I missing something?
>>
>> -David
>>
>> On Nov 29, 2017, at 11:09 PM, Remi Forax <[email protected]> wrote:
>>
>> Hi,
>> those constants are referenced by some invokedynamic instructions in the
>> bytecode.
>> When you see an invokedynamic instruction with the MethodVisitor at that
>> point, you can change the reference to the bootstrap method you want.
>>
>> cheers,
>> Rémi
>>
>>
>>
>> On November 29, 2017 9:54:48 PM GMT+01:00, David Dunkle <
>> [email protected]> wrote:
>>>
>>> After compiling with Java 8 and dumping the resulting class files with
>>> javap, I see this, of which I am only showing the first 2 items:
>>>
>>> BootstrapMethods:
>>>
>>>   0: #174 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:
>>> (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/
>>> lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/
>>> MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/
>>> invoke/MethodType;)Ljava/lang/invoke/CallSite;
>>>
>>>     Method arguments:
>>>
>>>       #175 (Ljava/lang/Object;)Z
>>>
>>>       #179 invokestatic llllll/lallll.lambda$printPersons$0:(Lllllll/
>>> lallll;)Z
>>>
>>>       #180 (Lllllll/lallll;)Z
>>>
>>>   1: #174 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:
>>> (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/
>>> lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/
>>> MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/
>>> invoke/MethodType;)Ljava/lang/invoke/CallSite;
>>>
>>>     Method arguments:
>>>
>>>       #175 (Ljava/lang/Object;)Z
>>>
>>>       #191 invokestatic llllll/lallll.lambda$printPersons$1:(Lllllll/
>>> lallll;)Z
>>>
>>>       #180 (Lllllll/lallll;)Z
>>>
>>>   2: #174 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:
>>> (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/
>>> lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/inv
>>>
>>>
>>> Can I use ASM to visit the instructions in these bootstrap methods and
>>> change, say, the names of the methods being called using invokestatic
>>> instructions above?
>>>
>>> Apparently these methods are not part of the normal methods of a class,
>>> and I haven't had any luck visiting them using standard ASM class and
>>> method techniques.
>>>
>>> thanks,
>>>
>>> -David
>>>
>>
>> --
>> Sent from my Android device with K-9 Mail. Please excuse my brevity.
>>
>>
>


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