Re: 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?

-David

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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