[Soot-list] PatchingChain.insertBefore(Chain<E> toInsert, E point): bug?

[Khilan Gudka]

Hi,

Sorry, my description of the problem was incorrect. All jumps to "point"
from any unit in the chain are redirected to the first unit in the chain.

Khilan

2009/12/12 Khilan Gudka <khilan at doc.ic.ac.uk>

> Hi Eric,
>
> I've just come across another issue, which the previous fix doesn't solve.
> If the first unit u of the chain being inserted itself points to "point",
> then the code still results in u then pointing to u. For example, inserting
>
> label0:
> if (x == 0) goto label1;
>
> before
> label1:
> nop
>
> would lead to:
>
> label0:
> if (x == 0) goto label0;
>
> label1:
> nop
>
> I had a look and found that AbstractUnit.redirectJumpsToThisTo(Unit
> newLocation) does not check if the jump source is itself "newLocation." Is
> this the intended behaviour?
>
> What do you suggest?
>
> Thanks,
> Khilan
>
> 2009/12/10 Eric Bodden <bodden at st.informatik.tu-darmstadt.de>
>
>> Seems to cause no problems... This is now committed in revision 3351.
>>
>> Thanks again,
>> Eric
>>
>> --
>> 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
>>
>>
>>
>> 2009/12/10 Eric Bodden <bodden at st.informatik.tu-darmstadt.de>:
>> > Hi Khilan.
>> >
>> > Thanks for the patch. This looks like a correct patch to an actual bug
>> > to me. I will try it out with our test suite today.
>> > Eric
>> >
>> > --
>> > 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
>> >
>> >
>> >
>> > 2009/12/9 Khilan Gudka <khilan at doc.ic.ac.uk>:
>> >> Hi,
>> >> The method PatchingChain.insertBefore(Chain<E> toInsert, E point)
>> inserts
>> >> the chain "toInsert" just before "point" in the receiver chain. It does
>> this
>> >> by calling PatchingChain.insertBefore(E toInsert, E point) for each
>> Unit in
>> >> a reversed version of toInsert. To keep the correct control flow,
>> >> PatchingChain.insertBefore(E toInsert, E point) redirects jumps to
>> "point"
>> >> to jump to "toInsert" instead. However, I've found that this leads to
>> bugs
>> >> when inserting a chain that contains jumps itself. For example,
>> inserting
>> >> the jimple code:
>> >>         if $r == 0 goto label0;
>> >>         staticinvoke <mypackage.MyClass: void m()>();
>> >>      label0:
>> >>         staticinvoke <mypackage.MyClass: void n()>();
>> >> Which corresponds to:
>> >> if($r) {
>> >>     MyClass.m();
>> >> }
>> >> MyClass.n();
>> >> Would be turned into the following when using the
>> >> above PatchingChain.insertBefore(Chain<E> toInsert, E point) method:
>> >>      label0:
>> >>         if $r == 0 goto label0;
>> >>         staticinvoke <mypackage.MyClass: void m()>();
>> >>         staticinvoke <mypackage.MyClass: void n()>();
>> >> The reason being that when insertBefore(E toInsert, E point) is
>> repeatedly
>> >> called, the jump to "staticinvoke <mypackage.MyClass: void n()>();" is
>> >> redirected to the first statement "if $r == 0 goto label0;".
>> >> I think the solution is to, lastly, redirect jumps to "point" to the
>> first
>> >> unit in toInsert (here is a snippet from the bottom
>> >> of PatchingChain.insertBefore(Chain<E> toInsert, E point) and the
>> proposed
>> >> changes are in bold):
>> >>         E previousPoint = point;
>> >>         Iterator<E> it = backwardList.iterator();
>> >>         while (it.hasNext())
>> >>         {
>> >>             E o = it.next();
>> >>             insertBeforeNoRedirect(o, previousPoint);
>> >>             previousPoint = o;
>> >>         }
>> >>         ((Unit) point).redirectJumpsToThisTo((Unit)
>> toInsert.getFirst());
>> >> Does this make sense or have I overlooked something?
>> >> Thanks,
>> >> Khilan
>> >> _______________________________________________
>> >> Soot-list mailing list
>> >> Soot-list at sable.mcgill.ca
>> >> http://mailman.cs.mcgill.ca/mailman/listinfo/soot-list
>> >>
>> >>
>> >
>>
>
>
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