[Soot-list] Add Expression works strange.

[Elena Sherman]

Eric, yes, it works correctly. I've added the print statement in Roman's
code and it does prints out 500. So, I don't know if it should be reported
or not.
When I was looking for the format of iinc_w I found the following
iinc_w index byte1 byte2
where the value to be incremented is calculated as byte1 << 8 | byte2
When I've changed the value to increment from 500 to  512 and  javap
changed the bytecode from "iinc_w        #0,  1" to "iinc_w        #0,  2",
so apparently javap shows only byte1 part since 1<<8 = 256 and 2<<8 is 512
but fails to show byte 2, which should be 244 for 500 and 0 for 512.

Roman, when you instrument the code make sure to add your instrumentation
before return statement, for example by using units.insertBefore(....) or
units.insertAfter(...) methods.


On Fri, Feb 6, 2015 at 5:37 AM, Eric Bodden <eric.bodden at sit.fraunhofer.de>
wrote:

> Thanks a lot for the input Elena!
>
> Wow, that's odd! I have never seen javap give such apparently
> false/misleading information. Is this something we should report to Oracle?
>
> Anyway, I would assume that the bytecode is actually correct?
>
> Cheers,
> Eric
>
>
> > On 06.02.2015, at 01:22, Elena Sherman <elenasherman at boisestate.edu>
> wrote:
> >
> > Roman,
> >
> > I've run your code with the initialization of the local variable part
> added to it. It looks like that depending on the bytecode viewer I get
> different bytecode. When I use javap -c Decomp.class I get the following
> (what you get):
> >
> > Compiled from "Decomp.java"
> > public class decomp.Decomp {
> >   public decomp.Decomp();
> >     Code:
> >        0: aload_0
> >        1: invokespecial #1                  // Method
> java/lang/Object."<init>":()V
> >        4: return
> >        5: iconst_0
> >        6: istore_0
> >        7: iinc_w        #0,  1              // #0
> >
> >   public static void main(java.lang.String[]);
> >     Code:
> >        0: return
> >        1: iconst_0
> >        2: istore_0
> >        3: iinc_w        #0,  1              // #0
> > }
> >
> > However, when I use Eclipse's bytecode viewer I get the following:
> >
> > // Compiled from Decomp.java (version 1.2 : 46.0, super bit)
> > public class decomp.Decomp {
> >   // Method descriptor #12 ()V
> >   // Stack: 1, Locals: 1
> >   public Decomp();
> >      0  aload_0 [this]
> >      1  invokespecial java.lang.Object() [1]
> >      4  return
> >      5  wide
> >      6  iinc 0 500 [this]
> >       Line numbers:
> >         [pc: 0, line: 0]
> >         [pc: 1, line: 1]
> >         [pc: 4, line: 2]
> >         [pc: 5, line: 3]
> >       Attribute: LineNumberTable Length: 18
> >       Attribute: LineNumberTable Length: 18
> >
> >   // Method descriptor #11 ([Ljava/lang/String;)V
> >   // Stack: 0, Locals: 1
> >   public static void main(java.lang.String[] arg0);
> >     0  return
> >     1  wide
> >     2  iinc 0 500 [arg0]
> >       Line numbers:
> >         [pc: 0, line: 0]
> >         [pc: 1, line: 1]
> >       Attribute: LineNumberTable Length: 10
> >       Attribute: LineNumberTable Length: 10
> > }
> >
> > Which is correct. So, apparently the wide incremental instruction, i.e.,
> iinc_w should be interpreted a bit different than its regular version iinc.
> I'm not a bytecode specialist, so I cannot tell exactly how to interpret
> iinc_w's arguments in terms of iinc.
> >
> > In general bytecode can be quite confusing, so in order to check whether
> your instrumentation works as expected try to print something out like the
> value of the local variable you're trying to increment. Thus when you
> execute the instrumented code you will know for sure if this is what you
> want or not, or there are any errors in the instrumentation.
> >
> > Hope it helps.
> >
> > Elena
> >
> > On Thu, Feb 5, 2015 at 11:38 AM, Roman Petriev <vvpiroman at gmail.com>
> wrote:
> > Test cases here.
> > Is it good? Do you need anything else?
> >
> > 2015-02-05 12:58 GMT+03:00 Bodden, Eric <eric.bodden at sit.fraunhofer.de>:
> > Hi Roman.
> >
> > > I hope that is (exactly) what you want to see.
> >
> > Ideal would be a minimal but runnable example, including your driver
> class for Soot and the command-line options you are using. We should be
> able to reproduce this with as little effort as possible.
> >
> > Thanks,
> > Eric
> >
> >
>
> --
> Prof. Eric Bodden, Ph.D., http://sse.ec-spride.de/ http://bodden.de/
> Head of Secure Software Engineering at Fraunhofer SIT, TU Darmstadt and EC
> SPRIDE
> Tel: +49 6151 16-75422    Fax: +49 6151 869-127
> Room B5.11, Fraunhofer SIT, Rheinstraße 75, 64295 Darmstadt
>
>
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