[Soot-list] Reachability in CFGs

[Chris Pickett]

irem wrote:
> First of all, thanks for the suggestions on visualizing the control flow
> graphs.
> 
> Actually, the reason I was interested in various predecessors and
> successors of nodes in control graphs is that I am interested in
> reachability. 
> 
> If we look at the following example:
> 
> m1();
> 
> try {
> m2();
> }
> catch (Exception e){
> m3();
> }
> 
> 
> A property such as "method m2 is always called before m3" holds for this
> program. But Soot constructs CFGs which concentrate on completed
> executions, hence there is an edge from the predecessor of the statement
> which calls m2 to the exception handler and it seems as if one can end
> up in the handler without calling m2. 

As an aside, what do you mean by "call"?  It is certainly possible for 
INVOKE* to throw an exception before m2 is actually entered.

http://java.sun.com/docs/books/jvms/second_edition/html/Instructions2.doc6.html#invokeinterface

I don't think that changes what you are trying to do below, but I 
thought I should mention it anyway.

Chris

> I think this was not the case for certain earlier versions, and I
> inherited a code that worked fine with them. But now I have to
> manipulate the CFGs given by soot to reflect reachability better.
> 
> Anyway, right now, what I do is to construct the ExceptionalUnitGraph,
> and check 
> for each node in the graph:
>  	for each of its exceptional successors in the graph:
> 		whether the successor is a handler unit for one of the 
> 		ExceptionalDests of the node
> 		if this is so, 
> 			I keep the edge between the node and successor 
> 		else
> 			I delete the edge
> 
> 
> 
> I have not tested this enough to see if it is correct. What does
> everyone think? 
> And would you think of integrating such an alternative graph to soot,
> i.e. through some option? I think many people may be interested in it.
> 
> Irem Aktug
> Ph.D. Student
> Stockholm, Sweden
> 
> 
> _______________________________________________
> Soot-list mailing list
> Soot-list at sable.mcgill.ca
> http://mailman.cs.mcgill.ca/mailman/listinfo/soot-list