[Soot-list] verification error on accessing fields

[Paris Yiapanis]

Hi again,

Problem solved. Finally it was the casting. Even though Jimple was showing
the casting, it wasn't doing it when converted back to bytecode.
Thanks for the help anyways.

I am still wondering though, (based on my previous email) why you cannot
access the fields of a superclass just by using the subclass (i.e. without
using the .getSuperClass() to access the fields).

Thanks,

Paris

On Thu, Jun 24, 2010 at 9:18 AM, Paris Yiapanis <yiapanip at cs.man.ac.uk>wrote:

> Hi,
>
> I think the problem has something to do with casting.
>
> For instance, I generate the following Jimple code:
>
>
> public void m()
> {
>         myPackage.MyClass r0;
>         java.lang.Object r1;
>         int[] r2;
>         myPackage.TempClass r3;
>
>         r0 := @this: myPackage.MyClass;
>         r1 = r0.<myPackage.MyClass: java.lang.Object objRef>;
>         r3 = (myPackage.TempClass) r1;
>
>         r2 = r3.<myPackage.TempClass: int[] a>;
>         ....
>         ....
>         return;
>   }
>
> At the statement "r3 = (myPackage.TempClass) r1;", Jimple shows that it
> casts 'r1'. However, if I check the bytecode produced from that,
> it doesn't actually have a 'checkcast' code. So I guess that the casting
> doesn't actually happen.
> I was trying to use the JCastExpr but I am not sure how it exactly works.
> I tried to create a JCastExpr(r1, myPackage.MyClass) but it complains that:
> Box VB(null) cannot contain value: r0.<myPackage.MyClass: java.lang.Object
> objRef>(class soot.jimple.internal.JInstanceFieldRef)
>
> Any ideas? Any help appreciated.
>
> Thanks
>
> - Paris
>
>
>
> On Wed, Jun 23, 2010 at 4:51 PM, Paris Yiapanis <yiapanip at cs.man.ac.uk>wrote:
>
>> Hi Eric,
>>
>> First of all thank you very much for your quick response. It is highly
>> appreciated.
>>
>> The package name is my mistake now while copying, but it is actually the
>> same in my code.
>>
>> I have tried the '-validate' option as you suggested but it didn't show
>> anything.
>>
>> The TempClass looks like:
>>
>> public class TempClass {
>>     public int[] a = new int[10];
>>     public int[] b = new int[10];
>>
>>     public TempClass(){
>>            initializeArrayA();
>>     }
>>
>>         public void m(){
>>
>>            for(int i= 0; i < a.length; i++){
>>                b[i] = a[i];
>>            }
>>
>>     }
>> }
>>
>> In my code I am generating from scratch a class myClass that gets a hold
>> of the 'this' reference of TempClass and accesses its fields.
>>
>> Now I had another issue that I do not know to what extend may be causing
>> the problem (and I hope I don't confuse the things):
>>
>> Inside myClass class as you can see from my Jimple earlier, I am accessing
>> an instance field 'objRef'.
>> However, objRef field is not declared inside myClass. It is declared in
>> another class called 'AbstractClass' which myClass extends.
>> So, while producing jimple I couldn't say:
>> myClass.getFieldByName('objRef'). It was complaining that 'myClass' doesn't
>> have such a field.
>> Thus I had to use the superclass to access that field:
>> myClass.getSuperclass().getFieldByName('objRef').
>>
>> I didn't mention that in my jimple code above to keep things simpler, but
>> the jimple statement is actually:
>> r1 = r0.<myPackage.*AbstractClass*: java.lang.Object objRef>;
>>
>> rather than:
>>
>> r1 = r0.<myPackage.*MyClass*: java.lang.Object objRef>;
>>
>> In reality I should have been able to use MyClass.objRef, isn't it?
>> I don't know if this contributes to my verification problem  later.
>> I hope I didn't make things more confusing.
>>
>>
>> Thank you in advance,
>>
>> Paris
>>
>> On Wed, Jun 23, 2010 at 4:14 PM, Eric Bodden <
>> bodden at st.informatik.tu-darmstadt.de> wrote:
>>
>>> By the way: why are you using different package names?
>>>
>>> testLoops2.TempClass in the cast but myPackage.TempClass in the field
>>> access.... may that be the mistake?
>>>
>>> Eric
>>>
>>> --
>>> Dr. Eric Bodden
>>> Software Technology Group, Technische Universität Darmstadt, Germany
>>> Tel: +49 6151 16-5478    Fax: +49 6151 16-5410
>>> Mailing Address: S2|02 A209, Hochschulstraße 10, 64289 Darmstadt
>>>
>>>
>>>
>>> On 23 June 2010 17:13, Eric Bodden <bodden at st.informatik.tu-darmstadt.de>
>>> wrote:
>>> >> Does anyone know any way around this problem, as I do not want to
>>> disable
>>> >> verification?
>>> >
>>> > Hmm, I don't see anything wrong. It may help to see the code of
>>> > TempClass... You may try the -validate switch to Soot. That will do
>>> > some validation on your Jimple code.
>>> >
>>> > Eric
>>> >
>>>
>>
>>
>
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