[Soot-list] duplicate subgraphs in CFG

[Martin Bravenboer]

Hi Hossein & Eric,

I'm not using the Soot Eclipse plugin, so I don't know if this code is
compiled by the Eclipse compiler or one of the Soot front-ends?

Anyway, it seems an issue specific to one of these compilers. If you
compile the code with javac, and use Soot to produce Jimple, then you
get this:

---------------------------------------------------------------------
    public static void main(java.lang.String[])
    {
        java.lang.String[] r0;
        java.io.PrintWriter r1, $r4;
        java.io.IOException r2, $r5;
        java.lang.Throwable r3, $r8;
        java.io.PrintStream $r6;
        java.lang.String $r7;

        r0 := @parameter0: java.lang.String[];
        r1 = null;

     label0:
        $r4 = new java.io.PrintWriter;
        specialinvoke $r4.<java.io.PrintWriter: void
<init>(java.lang.String)>("out.txt");
        r1 = $r4;
        virtualinvoke r1.<java.io.PrintWriter: void
println(java.lang.String)>("something");

     label1:
        if r1 == null goto label9;

        virtualinvoke r1.<java.io.PrintWriter: void close()>();
        goto label9;

     label2:
        $r5 := @caughtexception;

     label3:
        r2 = $r5;
        $r6 = <java.lang.System: java.io.PrintStream out>;
        $r7 = virtualinvoke r2.<java.io.IOException: java.lang.String
getMessage()>();
        virtualinvoke $r6.<java.io.PrintStream: void
println(java.lang.String)>($r7);

     label4:
        if r1 == null goto label9;

        virtualinvoke r1.<java.io.PrintWriter: void close()>();
        goto label9;

     label5:
        $r8 := @caughtexception;

     label6:
        r3 = $r8;

     label7:
        if r1 == null goto label8;

        virtualinvoke r1.<java.io.PrintWriter: void close()>();

     label8:
        throw r3;

     label9:
        return;

        catch java.io.IOException from label0 to label1 with label2;
        catch java.lang.Throwable from label0 to label1 with label5;
        catch java.lang.Throwable from label3 to label4 with label5;
        catch java.lang.Throwable from label6 to label7 with label5;
    }
}
---------------------------------------------------------------------

This is correct:

     label0: try code
     label1: finally code for successful try
     label2: exception handler for try (IOException)
     label3: catch code
     label4: finally code for successful catch
     label5: exception handler for try (all Throwable not IOException)
and any throwable in catch
     label7: finally code for failure in try or failure in catch

The handlers:

        catch java.io.IOException from label0 to label1 with label2;

IOException in try code -> goto catch

        catch java.lang.Throwable from label0 to label1 with label5;

Throwable in try code -> goto finally

        catch java.lang.Throwable from label3 to label4 with label5;

Throwable in catch code -> goto finally

        catch java.lang.Throwable from label6 to label7 with label5;

This exception handler is always generated by javac and seems to
handle corner cases. It covers astore_2 only, which can only throw
asynchronous exceptions (the instructions itself doesn't throw
anything). It retries the finally clause if an exception occurs.

Cheers,
-- 
Martin Bravenboer
---------------------------------------------------------------------
Department of Computer Science
University of Massachusetts Amherst