[Soot-list] Reachability in CFGs

[irem]

Ok, my mistake there. Sure the invoke instruction may raise an
exception. True, this we are not ruling out. Bad example.

irem    

On Sun, 2007-11-04 at 16:51 -0500, Chris Pickett wrote:
> 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
> > 
> > 
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