Re: Incorrect Parameter Order

Thanks for the javap tip.  I figured out the problem (I shouldn't use
visietMethodInsn because that will add the println to where I call trace,
instead of adding the println inside the trace function).

Another question, assume my class has a method called "foo" and "trace".
Can I obtain Method objects that represent these method ?  So that I can
quickly get information about parameter, types etc of the methods.

@Eliot  I want to use ASM because I might not have the program src code as
input,  just the class file (compiled with debugging info).  Currently I am
learning ASM so I just use some simple examples that can be done by just
parsing the src directly.

On Fri, Dec 1, 2017 at 9:33 PM Eliot Moss <[email protected]> wrote:

> On 12/1/2017 6:30 PM, ThanhVu (Vu) Nguyen wrote:
> > I want to instrument a function to print out its parameter values
> > For example,  void trace(b,d){}   becomes  void
> trace{System.out.println(b+ " " + d);}
> >
> > And trace is invoked from another function, e.g.,
> > foo(){
> >     int a = 0;
> >     int b = 1;
> >     int c = 2;
> >     int d = 3;
> >     trace(b,d);
> > }
> >
> > So after the instrument I want the program to print
> > 1 3  when running foo
> >
> > I wrote some code for ASM to do it, but I did it wrong because it always
> print
> > 0 1  (i.e., . the values of a and b.  I suspect I didn't use the correct
> arg index, but I am not
> > sure how to make it right.
> >
> > Essentially my code contains a loop in visitMethodInsn that prints
> something like
>
> I think you probably meant:
>
> void trace(int b, int d) {} ==>
> void trace(int b, int d) {System.out.println(b+" "+d);}
>
> Somewhat agreeing with a previous responder, you can simply write that out,
> compile it, and use javap to see the bytecode the compiler produces.
>
> I will guess that your problem is that you meant for the trace method to
> be static.  If it is not static, then local 0 is "this" and b will be in
> local 1, etc.
>
> I also wonder if what you're doing overall is generating this class using
> a program, a program that extracts the various desired forms from other
> program text.  If you're doing that, then you could just have that program
> generate the source code and run it through javac rather more easily than
> doing this task with ASM.  (A reason to do it with ASM is if you want to
> build a class file on the fly and pass it into a running a VM.)
>
> Regards - Eliot
>
> --
> You receive this message as a subscriber of the [email protected] mailing list.
> To unsubscribe: mailto:[email protected]
> For general help: mailto:[email protected]?subject=help
> OW2 mailing lists service home page: http://www.ow2.org/wws
>


-- 
You receive this message as a subscriber of the [email protected] mailing list.
To unsubscribe: mailto:[email protected]
For general help: mailto:[email protected]?subject=help
OW2 mailing lists service home page: http://www.ow2.org/wws