Re: NPE in FrameNode

Npe's in asm are not uncommon and in my experience are caused by not  
all properties being set on the method or the internals of the method.

Try to use the debug jar instead of the normal one because stacktraces  
are missing debug info. After you have replaced the jar, run again,  
and go to the method that causes the npe. In most cases i'm able to  
figure out what is missing.



On 25 feb 2010, at 13:22, melix <[email protected]> wrote:

>
> Hi,
>
> I'm new to ASM, so there must be many things I'm missing. I'm trying  
> to
> replace a method with another. I've written code for the new method,  
> and
> looked at the bytecode outline to see what's generated for it. At  
> the end of
> the method, I can see the following :
>
> L9
>    LINENUMBER 227 L9
>   FRAME CHOP 1
>    ICONST_0
>    IRETURN
>
> This actually gets converted to the following ASM code :
>
> mv.visitLabel(l9);
> mv.visitLineNumber(227, l9);
> mv.visitFrame(Opcodes.F_CHOP,1, null, 0, null);
> mv.visitInsn(ICONST_0);
> mv.visitInsn(IRETURN);
>
> However, if I use a MethodNode as the method visitor, then the  
> following
> exception is thrown :
>
> Exception in thread "main" java.lang.NullPointerException
>    at java.util.Arrays$ArrayList.<init>(Arrays.java:3357)
>    at java.util.Arrays.asList(Arrays.java:3343)
>    at org.objectweb.asm.tree.FrameNode.asList(Unknown Source)
>    at org.objectweb.asm.tree.FrameNode.<init>(Unknown Source)
>    at org.objectweb.asm.tree.MethodNode.visitFrame(Unknown Source)
>
> Is it a bug in ASM (FrameNode ? MethodNode ?), in ASMifier, or in my  
> own
> code ? Is there any workaround ?
>
> BTW, I'm using ASM 3.2.
>
> Thanks a lot,
>
>
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>
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