Re: instrumenting try block

Hi,

18/07/2011 18:56, Yudi Zheng wrote:
> Hi,
>
> We are trying to insert new code section into existing exception handler.
> In an example below is just simplified scenario, but we are using similar
> code to insert try-finally into methods.
>
> We have encountered buggy behavior when using COMPUTE_FRAMES
>   in conjunction with COMPUTE_MAXS within ClassWriter.
>
> The following code (for full runnable code see attachments) produces
> Java VerifyError. If we use the Class writer twice in a row at the end,
> the produced result is as expected.
>
> Do you have any idea, what can cause the error?

>     ilst.insert(handler, new IntInsnNode(Opcodes.ALOAD,
>     method.maxLocals));
>     ilst.insert(handler, new IntInsnNode(Opcodes.ASTORE,
>     method.maxLocals));

the error is that you used IntInsnNode instead of VarInsnNode. This type 
of error can easily be detected with a CheckClassAdapter:

// Transform into bytecode
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
ClassVisitor cv = new CheckClassAdapter(cw);
cn.accept(cv);

Eric

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