Re: Error in changed bytecode

Hello,

I think your error is that you're forgetting that longs and doubles take two
"slots" on the stack and on the locals, so you have to space them
accordingly -- i.e., when you LSTORE 11, you occupy 11 and 12, and if you
previously LSTORED to 10, you've clobbered half your long.

You might want to code a simple java method that stores multiple longs in
local variables to see what is the generated bytecode.

Ivo

On Sun, Jul 24, 2011 at 2:37 PM, Jayanga Wagaarachchi <
[email protected]> wrote:

> Hi,
>
> I am having a confusing error when I tried to add some code to calculate
> time consumed by a section of method. I am adding some bytecodes. But when I
> run the changed program I receive an error An unexpected error has been
> detected by Java Runtime Environmen# EXCEPTION_ACCESS_VIOLATION
> (0xc0000005)# Java VM: Java HotSpot(TM) Client VM (1.6.0-b105 mixed mode,
> sharing)
>
> Then I tried to analyze the code using *CheckClassAdapter. *when I am
> trying to verify the code it shows me an error in the changed byte code as Expected
> J, but found . I figured this is caused when accessing uninitialized
> variable.  here is a part of output from CheckClassAdapter
>
> 00072 LOriginal; [[I [[I [[I I I I . . . J . . . . .  :  :    L1
> 00073 LOriginal; [[I [[I [[I I I I . . . J . . . . .  :  :    FRAME FULL
> [Original [[I [[I [[I I I I T T T J] []
> 00074 LOriginal; [[I [[I [[I I I I . . . J . . . . .  :  :     INVOKESTATIC
> java/lang/System.nanoTime ()J
> 00075 LOriginal; [[I [[I [[I I I I . . . J . . . . .  : J  :     LSTORE 11
> 00076 LOriginal; [[I [[I [[I I I I . . . . J . . . .  :  :     LLOAD 11
> 00077 LOriginal; [[I [[I [[I I I I . . . . J . . . .  : J  :     LLOAD 10
> 00078 ?                       :     LSUB
>
> Here if you look at the instruction 75 which is LSTORE 11 at that point I
> have already added anther long value initialized and stored at position 10.
> But when the LSTORE 11 executes the long value at the position 10 disappears
> causing the above mentioned error at instruction 77. Isn't this confusing? I
> am stuck at this point because I cant find any reason why this happens.
>
> Can you show me what is wrong here?
> Thank you.
> --
> Jayanga Wagaarachchi
> Computer Science and Engineering
> University of Moratuwa.
>
>
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