Re: Re: ClassReader exception due to bad bytecode

javap and ASM tell you the same thing, the way you encode your class name
(when you call ClassVisitor.visit(...)) is wrong.

Usually it's because you use null as argument of visit().

Rémi

On 01/26/2011 05:57 AM, Buu Vinh wrote:
> Thanks for the suggestion. The result of javap - v -p as following:
>
> Exception in thread "main" java.lang.NullPointerException
>         at 
> sun.tools.javap.JavapPrinter.javaclassname(JavapPrinter.java:856)
>         at 
> sun.tools.javap.JavapPrinter.printclassHeader(JavapPrinter.java:62)
>         at sun.tools.javap.JavapPrinter.print(JavapPrinter.java:38)
>         at sun.tools.javap.Main.displayResults(Main.java:202)
>         at sun.tools.javap.Main.perform(Main.java:61)
>         at sun.tools.javap.Main.entry(Main.java:49)
>         at sun.tools.javap.Main.main(Main.java:34)
>
> I can't tell what is wrong with my bytecode based on the above 
> messages. I would guess the problem is in the header, is it a wild 
> guess? Are there tools that help to identify problems in the bytecode? 
> Please advice.
>
> --- On *Tue, 1/25/11, Dave Brosius /<[email protected]>/* wrote:
>
>
>     From: Dave Brosius <[email protected]>
>     Subject: Re: [asm] ClassReader exception due to bad bytecode
>     To: [email protected], [email protected]
>     Date: Tuesday, January 25, 2011, 7:20 PM
>
>     Does javap -v -private YourClass
>
>     produce anything different?
>
>     On 01/25/2011 04:54 PM, Buu Vinh wrote:
>>     After using ASM 3.2 for the bytecode instrumentation, I tried to
>>     verify the result by feeding the transformed bytecode to
>>     ClassReader and invoking ASMifierClassVisitor:
>>     .........
>>     cr = new ClassReader(originalBytes);
>>     cw = new ClassWriter(cr,ClassWriter.COMPUTE_MAXS);
>>     BciClassAdapter bca = new BciClassAdapter(cw, iClass);
>>     cr.accept(bca, 0);
>>     byte[] newBytes = cw.toByteArray();
>>
>>     ClassReader cr = new ClassReader(newBytes);
>>     File tmpFile = new File(fileName);
>>     File tmpDir = tmpFile.getParentFile();
>>     tmpDir.mkdirs();
>>     ClassVisitor cv = new ASMifierClassVisitor(new PrintWriter(tmpFile));
>>     cr.accept(cv, 0);
>>     ........
>>
>>     I got ClassReader Exception when processing "newBytes":
>>
>>     java.lang.ArrayIndexOutOfBoundsException: Array index out of
>>     range: 51966
>>      at com.bv.asm.ClassReader.readUTF8(ClassReader.java:1946)
>>      at com.bv.asm.ClassReader.readClass(ClassReader.java:2015)
>>      at com.bv.asm.ClassReader.getClassName(ClassReader.java:229)
>>      at
>>     com.bv.bci.instrument.InstrumentClass.verify(InstrumentClass.java:287)
>>
>>
>>     Apparently ClassReader was not able to parse "newBytes", I
>>     assumed that "newBytes" was ill-formated due to some kind of
>>     problem in my bytecode instrumenation, but I could not locate the
>>     error. I used ClassWriter.COMPUTE_MAXS, but it did not help.
>>     Please advice. Thanks
>>
>

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