[Soot-list] invokedynamic/lambda support

[Steven Arzt]

Hi Brian,

Invokedynamic support in Soot is somewhat limited at the moment. There 
are people working on extending it to cover more cases, but that's still 
work in progress. Adding more methods to the fake Invokedynamic class is 
an option, but keep in mind that your analyses also need to be aware of 
the semantics of these new functions. Additionally, if you want to write 
the code back out, the backends also need a way to deal with these new 
methods. Depending on what you are trying to achieve, this solution 
might be good enough, though. The allow-phantom-refs is essentially a 
generalization of that idea: Whenever Soot encounters a method reference 
for a method it does not know, it will create a fake method for it, a 
"phantom".

The Jasmin backend is totally outdated for various reasons. Use the 
-asm-backend command-line option to enable the much newer and better ASM 
backend. It will become the default pretty soon anyway.

Best regards,
   Steven

On 2016-11-15 21:29, Brian Alliet wrote:
> I've been having some trouble getting Soot to process any file
> containing lambdas. Even the most trivial example:
> 
> public class Lambda {
> // intentionally avoiding any external dependencies on 
> java.util.function
>      @FunctionalInterface
>      public interface IntPredicate { public boolean test(int value); }
>      public static boolean even(int x) {
>          return ((IntPredicate) (y -> y  % 2 == 0)).test(x);
>      }
> };
> 
> fails with:
> 
> soot.SootMethodRefImpl$ClassResolutionFailedException: Class
> soot.dummy.InvokeDynamic doesn't have method test([]) :
> Lambda$IntPredicate; failed to resolve in superclasses and interfaces
> Looking in soot.dummy.InvokeDynamic which has methods []
> 
> I managed to hack around this by doing:
> 
>>                             SootMethod dummy = new 
>> SootMethod(insn.name,
>>                                     parameterTypes,
>>                                     returnType,
>>                                     soot.Modifier.ABSTRACT |
>> soot.Modifier.STATIC);
>> if(!bclass.declaresMethod(dummy.getSubSignature()))
>>                                 bclass.addMethod(dummy);
> 
> 
> In AsmMethodSource's convertInvokeDynamicInsn (bclass is
> SootClass.INVOKEDYNAMIC_DUMMY_CLASS here). This actually allows it to
> mostly succeed, however I realize just randomly adding abstract methods
> to soot.dummy.InvokeDynamic is probably wrong and certainly won't get 
> me
> the right semantics.  -allow-phantom-refs also seems to push the 
> example
> though (although I get the impression that may have other bad side 
> effects).
> 
> Is this expected to work? Am I doing something wrong?
> 
> Additionally, the Jasmin backend seems to choke on the invokedynamic
> instructions:
> 
> Jasmin:21: Warning - Syntax error.
>      invokedynamic "test" ()LLambda$IntPredicate;
> java/lang/invoke/LambdaMetafactory/metafactory(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;((Ljava/lang/Class;)class\blank"(I)Z",(Ljava/lang/invoke/MethodHandle;)handle:\
> 
> Using -asm-backend, seems to work though.
> 
> Thanks for any help,
> 
> -Brian
> 
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