[Soot-list] Split units in Jimple / missing equals-implementation

[Eric Bodden]

Hi.

This week I implemented a "must reaching definitions" analysis, i.e. a
definition os reachable from a use when it is reachable on *all* paths.
Strangely, this analysis missed the following case:

		int j;
		try {
			j=3;
		} catch(Throwable t) {
			j=4;
		} finally {
			j=5;
		}
		
		//why is j here not 5 FOR SURE?
		System.out.println(j); //(1)
		

Actually, the definition for j has definetely one unambigous reachable
definition: j=5. However, Soot splits this definition into multiple ones
in the exceptional unit graph. Since AssignStmt also does not implement
hashcode/equals, the intersection at line (1) fails, i.e. throws the
information j=5 away.

So am I missing something or is there something wrong?

I would suggest to fix this somehow, in one of the two following ways:

1.) Prevent ExceptionalUnitGraph from creating multiple different units
for entities that used to be the same on the source/bytecode level (i.e.
share them).
2.) Implement hashcode/equals on units.

Maybe both should be done.

Does this make sense?

Eric



--
Eric Bodden
Sable Research Group, McGill University
Montreal, Canada