[Soot-list] Help with NPE PointsToAnalysis.reachingObjects(Context, Local) using Heros/Spark+Geom

[Richard Xiao]

Hi, Pedroza:

Yes, your usage is wrong. Context means callsite in current implementation
of Geom PTA. And in Spark, context version of reachingObjects is not
supported.

You cannot observe the changes before/after the assignment with a
flow-insensitive points-to analysis, because the points-to results for the
pointer before/after the assignment are the same. You can only inspect what
are returned by "doSomethingElse".

Cheers,
Xiao



On Mon, May 20, 2013 at 10:30 PM, Henddher Pedroza <hpedro2 at uic.edu> wrote:

> Thank you Richard,
>
> So I am using reachingObjects incorrectly in this case? (because I am
> using the wrong statement?)
> (Thus far, I am experimenting with every possible 'reachingObjects' call
> to see what I get back and it seems like in this particular stmt the use is
> invalid, right?)
>
> In reality I am trying to get points-to-analysis for fields of
> instances: this.dummy
>
> I want to see what a field may be pointing to whenever an assignment
> involves that field. IOW, whenever there's an stmt with a field being set
> or being retrieved, I want to see what the field may point to before/after
> the assignment.
> Is such possible?
>
> Thanks
>
> On May 20, 2013, at 9:03 AM, Richard Xiao <richardxx at cse.ust.hk> wrote:
>
> Hi, Pedroza:
>
> The first argument of "reachingObjects" is the callsite that invokes the
> enclosing method of the second argument. For your case, context should be
> the statement "anObj.doSomething();". Please try again.
>
> Cheers,
> Xiao
>
>
>
> On Mon, May 20, 2013 at 9:48 PM, Henddher Pedroza <hpedro2 at uic.edu> wrote:
>
>> Hello,
>>
>> Any suggestions?
>>
>>
>> On May 17, 2013, at 10:58 AM, Henddher Pedroza <hpedro2 at uic.edu> wrote:
>>
>> Hello all:
>>
>> Using Heros in combination with SPARK w/Geom (*), I am getting an NPE in
>> CallGraph.findEdge(Unit, SootMethod) @ line 123 called from
>> GeomPointsTo.reachingObjects(Context, Local) @ line 1504:
>>
>> (*) cmd-line options:
>> -p cg
>> all-reachable:true,verbose:true,safe-forname:true,safe-newinstance:true -p
>> cg.spark enabled:true,verbose:true,geom-pta:true,geom-eval:2
>>
>> GeomPointsTo.reachingObjects(Context, Local):
>> 1504: Edge e = Scene.v().getCallGraph().findEdge((Unit)c, callee);
>>
>> CallGraph.findEdge(Unit, SootMethod):
>>     Edge findEdge( Unit u, SootMethod callee )
>>     {
>>     Edge e = srcUnitToEdge.get(u);
>> 123:  while ( e.srcUnit() == u && // <<<< NPE, e is null
>>
>> For my test, I am using one explicit entry point, discarding all default
>> entry-points configured by Soot.
>> My entry-point is a static method (staticFakeEntryPoint) which
>> instantiates one obj of the class I am testing. Then, in my interesting
>> method doSomething(), I perform a field assignment and request
>> PointsToAnalysis.reachingObjects(Context, Local) (see "<<<<" below).
>> Context is the current statement "stmt" (r0.<MyClass: java.lang.String
>> dummy> = $r3) and Local is "r0" (obtained
>> through stmt.getDefBoxes().getValue().getBase() more or less)
>>
>> MyClass {
>>    String dummy;
>>    void static staticFakeEntryPoint() {
>>       MyClass anObj = new MyClass();
>>       anObj.doSomething();
>>    }
>>    void doSomething() {
>>      this.dummy = doSomethingElse(); // <<<< jimple: r0.<MyClass:
>> java.lang.String dummy> = $r3
>>    }
>> }
>>
>> Am I incorrectly using pointsToAnalysis.reachingObjects(Context, Local)
>> or incorrectly configuring Spark?
>>
>> Why would srcUnitToEdge be lacking that edge?
>>
>> Any help is appreciated.
>>
>> - Henddher
>>
>>
>>
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>>
>>
>
>
> --
> Richard Xiao Xiao
> PhD Student @ CSE @ Hong Kong University of Science and Technology
> www.cse.ust.hk/~richardxx
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-- 
Richard Xiao Xiao
PhD Student @ CSE @ Hong Kong University of Science and Technology
www.cse.ust.hk/~richardxx
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