[Soot-list] Issue with trap generation in Jimple

[John Jorgensen]

>>>>> "eric.bodden" == Eric Bodden <eric.bodden at ec-spride.de> writes:

    eric.bodden> I actually got this resolved. It turns
    eric.bodden> out that ExceptionalUnitGraph already has a
    eric.bodden> boolean argument to its constructor that let's
    eric.bodden> one control the semantics exactly for this
    eric.bodden> case. I actually wonder whether we should not
    eric.bodden> change the default, though.

First, thanks for giving my ego a boost (I'm the one who included 
the omitExceptingUnitEdges parameter in the ExceptionalUnitGraph
constructor some nine years ago).

Second, though my knowledge of Soot is rusty enough that I'm not
confident about what I'm about to say, I'm not sure that
omitExceptingUnitEdges will solve your typing problem in the
most general case.

Let's change the assignment in your example so that its RHS is a
method invocation (one of the consequences of my stale knowledge
of soot is that I'm not sure such jimple can actually be
generated from real bytecode):

     label5:
        $u0 = someMethodOrOther();
        return $u0;

     label6:
        $u1 := @caughtexception;
        exitmonitor $u0;
        throw $u1;

        catch java.lang.Throwable from label2 to label5 with label6;

Now the assignment to $u0 has potential side effects, so even if
omitExceptingUnitEdges is true, there will be an exceptional edge
from the assignment itself to the handler (since the
ExceptionalUnitGraph constructor knows nothing about what
someMethodOrOther() does, it conservatively assumes that it might
modify something that the exception handler cares about).

There's more on this issue in section 2.4 (and especially 2.4.1)
of Sable technical report 2003-3.

-- 
John Jorgensen    <jorgnsn at cs.uregina.ca>    306.337.2344