I assume that you are talking about SmartLocalDefs, used by the ReachingDefsTagger? If so, then the following holds: SmartLocalDefs gives you the reaching definitions of local variables. When area is a local variable then print(…) obviously cannot write to it. Local variables can only be written to within the local method. They are, effectively, stack locations. Your advisor Lori is right in the case where area is a field, but SimpleLocalDefs only gives information for local variables. Hope that clarifies things…

Eric

A small continuation of the doubt in my previous comment.

The simple reaching def tagger that comes off the shelf with soot, simply ignores
outgoing calls? Is that correct behaviour? My advisor Lori Pollock told me that conservatively a reaching def tagger must warn
you that the value could be modified within the call (please see the example)

Thanks
Giri

I am sorry to trouble you again, but I did not find a suitable answer in the
survivor’s guide or the PLDI tutorial slides etc.

My issue is with reaching defs. Soot does intra-procedural reaching defs. But what
exactly does it do when it encounters a method call?

Ex:

1 area = initialize();
2 area = computeArea();
3 print (area);
4 return area;

Soot tells (correctly) that the def on line 2 (but not line 1) reaches line 4. BUT how
did it know that line 3 did not assign to area? (assume area is a field or
can be changed within print)

Thanks
Giri

Best Wishes
Giri

Eric

Thanks for these nice posts about SOOT. I am beginning to use SOOT for some
simple data flow analysis in my research (I am trying to do a PhD in CS at
University of Delaware, USA)

I used SOOT to do the reaching def analysis and got expected results. I have a doubt
about the following:

public int m1() // in a class C1
{
init();
return field1; // field is an integer field in the C1
}

private void init()
{
field1 = 5;
}

the above assignment provides a definition for field1 that reaches the return
statement in m1(). The default Jimple Annotation pack reaching def
did not show this (though I did select inter-procedure and entire program
mode). Am I missing something here?

Thanks a lot!
Giri