Debug NoClassDefFoundError

[Christian Beikov]

Thanks so much for this David Holmes! This flag is awesome!

Why are these exceptions not attached as suppressed exceptions on the 
NoClassDefFoundError? That would certainly help a lot of users. In my 
case, I am missing a few read-edges for the module descriptor.

Am 18.05.2021 um 04:51 schrieb David Holmes:
> On 18/05/2021 2:19 am, Christian Beikov wrote:
>> Hi,
>>
>> not sure if this is the right place to ask, so if I am wrong, please 
>> let me know where to ask this.
>>
>> I have a very strange problem with a generated class defined 
>> dynamically into a module through `MethodHandles.Lookup.defineClass`. 
>> When I try to instantiate it, I get a 
>> `java.lang.NoClassDefFoundError: Could not initialize class ...` 
>> without any further context:
>
> You get that exception when a class has been placed in the erroneous 
> state, which means that a previous attempt to initialize the class has 
> failed. As Remi indicated if you don't see that original exception it 
> is typically because something else has swallowed it. If the class is 
> dynamically generated such that there is no source code for you to 
> modify to debug the static initialization problem, then try running 
> with -Xlog:exceptions=trace to see if that shows you what the earlier 
> exception was.
>
> Cheers,
> David
>
>>
>>      at 
>> java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native 
>> Method)
>>      at 
>> java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) 
>>
>>      at 
>> java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) 
>>
>>      at 
>> java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
>>
>> Does anyone know how to further debug this? I was trying to find 
>> instructions for debugging the JVM itself but couldn't so far.
>>
>> Regards,
>>
>> Christian
>>
>>