Re: Adding try/finally block

Hi,

seems to be a known issue. Found the answer in this archive entry:
http://mail-archive.ow2.org/asm/2008-02/msg00037.html
Adding an artificial try block start label fixes the NPE.

Cheers Nikolas

Am Fr 30.04.2010 16:30 schrieb Nikolas Nehmer
<[email protected]>:

>Hi,
>
>I'm trying to add a try/finally block to every method in my system.
>Unfortunately I have to do so, to ensure a counter to set/reset
>properly
>in every case - i.e. normal execution of a method, exception raised in
>a
>specific method (i.e. athrow executed in the same method) and methods
>terminated by exception propagation.
>
>Conceptually I'm trying to do the following:
>methodStartLabel
>...
><<<counter increment injected manually before every return statement
>methodReturnStatement
><<<inject code here
><<<newTryBlockEndLabel
><<<counterIncrement
><<<athrowStatement
>methodEndLabel
>
>
>the TryCatckBlockNode is created with the following parameters:
>methodStartLabel, newTryBlockEndLabel, newTryBlockEndlabel, null
>
>For most cases I just don't use the visitor pattern, but inject the new
>statements into the instruction list directly. Accordingly, I add the
>TryCatchBlockNode just created into the tryCatchBlocks list. While
>executing the instrumented application the following
>NullPointerException is raised :( Any ideas or suggestions? I know
>there
>is an example in one of the ASM papers related to my usecase.
>Unfortunalty this doesn't help me a lot.
>
>java.lang.NullPointerException
>   at org.objectweb.asm.MethodWriter.visitMaxs(Unknown Source)
>   at org.objectweb.asm.tree.MethodNode.accept(Unknown Source)
>   at

>>de.kl.uni.cs.nehmer.setup.bci.SimpleBCIMethodAdapter.visitEnd(SimpleBCIMethodAdapter.java:51)
>   at org.objectweb.asm.ClassReader.accept(Unknown Source)
>   at org.objectweb.asm.ClassReader.accept(Unknown Source)
>   at
>de.kl.uni.cs.nehmer.setup.bci.BCIAgent.transform(BCIAgent.java:32)
>   at

>>sun.instrument.TransformerManager.transform(TransformerManager.java:169)
>   at

>>sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:365)
>   at java.lang.ClassLoader.defineClass1(Native Method)
>   at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
>   at
>java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
>   at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
>   at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
>   at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
>   at java.security.AccessController.doPrivileged(Native Method)
>   at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
>   at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
>   at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
>   at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
>   at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
>
>cheers Nikolas
>

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