Re: Re: Re: ClassReader exception due to bad bytecode

A lot of issues can be caught if you put CheckClassAdapter in the visitors
chain before ClassWriter.

  regards,
  Eugene
 On 2011-01-26 8:53 AM, "Rémi Forax" <[email protected]> wrote:
> 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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