Re: [xmlvm-users] Try catch crashes

[Gergely K. <ger...@ma...>]

Hi,

Would it makes sense to add DEX, the Android bytecode format as a new
"source language" to xmlvm?
Since it is already designed to execute on a register machine, it might be
easier to implement.

Best Regards,
Gergely

2009/11/19 Arno Puder <ar...@pu...>

>
> that is a known bug. Flow control in the JVM is represented by absolute
> jumps which we simply map to gotos in Objective-C. Exceptions sometimes
> cause the problems you are experiencing. We have discussed for a long
> time to convert the stack machine to register machine that would also
> reverse engineer flow control by removing the gotos. This is no easy
> matter and is further down on our to-do list. In the meantime you can
> probably get around the problem by inserting a dummy statement just
> before the try. Something like:
>
>   } else {
>        int x = 42;
>        try {
>
> Arno
>
>
> Markus Heberling wrote:
> > Hi,
> >
> > I have the following java code:
> >
> >         if(args==null){
> >                    System.out.println(1);
> >         }else{
> >             try{
> >                 System.out.println(2);
> >
> >             }   catch(Exception e){
> >                 System.out.println(3);
> >
> >             }
> >         }
> >
> > It gets converted to the following ObjectiveC code (only relevant part
> here)
> >
> >     if (_op1.o != [NSNull null]) goto label0;
> >     _op1.o = [java_lang_System _GET_out];
> >     _stack[_sp++].o = _op1.o;
> >     _stack[_sp++].i = 1;
> >     _sp -= 2;
> >     [((java_io_PrintStream*) _stack[_sp].o) println___int:_stack[_sp +
> 1].i];
> >     goto label1;
> >     @try {
> >     label0:;
> >     _op1.o = [java_lang_System _GET_out];
> >     _stack[_sp++].o = _op1.o;
> >     _stack[_sp++].i = 2;
> >     _sp -= 2;
> >     [((java_io_PrintStream*) _stack[_sp].o) println___int:_stack[_sp +
> 1].i];
> >     } @catch (java_lang_Exception* _ex) {
> >         _stack[_sp++].o = _ex;
> >         goto label7;
> >     }
> >
> > This code crashes. The label0 is inside the try and the code jumps into
> it from the outside. This seems not to be allowed in ObjectiveC. if I move
> the label0:; before the try manually, it works. The xsl would need to be
> changed, so that if there is a jvm:label directly after a jvm:catch, they
> have to be swapped. I tried but wasn't able to do this myself. Don't know if
> it has any side effects, too :/
> >
> > Markus
> >
> >
> > ------------------------------------------------------------------------
> >
> >
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-- 
Kis Gergely
MattaKis Consulting
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