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

Per Eugene's suggestion, I put CheckClassAdapter in the visitors chain before ClassWriter as following:
......
cr = new ClassReader(originalClassBytes);
cw = new ClassWriter(cr,ClassWriter.COMPUTE_MAXS);
BciClassAdapter bca = new BciClassAdapter(new CheckClassAdapter(cw), iClass);
cr.accept(bca, 0);
byte[] newBytes = cw.toByteArray();
.....

I used MethodVisitor.visitMaxs(0,0) in conjunction with ClassWriter(cr,ClassWriter.COMPUTE_MAXS) so that the max locals and max stacks can be automatically computed. However, CheckClassAdapter complained with the following error message:

java.lang.RuntimeException: Data flow checking option requires valid, non zero maxLocals and maxStack values

I then used visitMaxs(maxStacks,maxLocals) hoping that they will be override by ClassWriter(cr,ClassWriter.COMPUTE_MAXS), but CheckClassAdapter complained with the following message:

java.lang.RuntimeException: Error at instruction 2: Insufficient maximum stack size....

How do I get around the above problem without having to manually compute maxStacks and maxLocals? Please advice. Thanks

--- On Wed, 1/26/11, Eugene Kuleshov <[email protected]> wrote:

From: Eugene Kuleshov <[email protected]>
Subject: [asm] Re: Re: Re: ClassReader exception due to bad bytecode
To: [email protected]
Date: Wednesday, January 26, 2011, 7:57 AM

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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