RFR: 8243290: Improve diagnostic messages for class verification and redefinition failures

[Harold Seigel]

Hi Poonam,

Thanks for making this change.

In verifier.cpp, if ex_msg is NULL, will the call to st->print_cr() at 
line 142 - 143, fail?

Thanks, Harold

On 6/9/2020 10:46 AM, Poonam Parhar wrote:
> Hello,
>
> Please review this simple change for improving diagnostics around 
> class verification and linking failures:
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8243290
> Webrev: http://cr.openjdk.java.net/~poonam/8243290/webrev.00/
>
> Problem: During the class redefinition process, if a class 
> verification fails because it could not find a class referenced in the 
> class being redefined, the printed NoClassDefFoundError error message 
> is not very helpful. It does not print the class name for which 
> NoClassDefFoundError was encountered, and that makes it very hard to 
> find the real cause of redefinition failure.
>
> The proposed solution prints the class name during class linking and 
> verification failures. Example output produced with these changes:
>
> With 'redefine' tag:
>
>      [java] [3.243s][debug][redefine,class,load        ] loaded 
> name=org.apache.commons.logging.impl.Jdk14Logger (avail_mem=819540K)
>      [java] [3.243s][debug][redefine,class,load        ] loading 
> name=org.apache.commons.logging.impl.Log4JLogger kind=101 
> (avail_mem=819540K)
>      [java] [3.244s][info ][redefine,class,load,exceptions] link_class 
> exception: 'java/lang/NoClassDefFoundError org/apache/log4j/Priority'
>      [java] Java Result: 1
>
> With 'verification' tag:
>
>      [java] [49.702s][info ][verification] Verification for 
> org.apache.commons.logging.impl.Log4JLogger has exception pending 
> 'java.lang.NoClassDefFoundError org/apache/log4j/Priority'
>      [java] [49.702s][info ][verification] End class verification for: 
> org.apache.commons.logging.impl.Log4JLogger
>
>
> Improved error message:
>
>      [java] Exception in thread "main" java.lang.InternalError: class 
> redefinition failed: invalid class
>      [java]     at 
> java.instrument/sun.instrument.InstrumentationImpl.retransformClasses0(Native 
> Method)
>      [java]     at 
> java.instrument/sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:167)
>      [java]     at Main.main(Unknown Source)
>
>
> Thanks,
> Poonam
>