JDK 15 hidden classes & stack trace visibility

[Mandy Chung]

Can you use StackWalker with StackWalker.Option::SHOW_HIDDEN_FRAMES to 
programmatically find the appropriate frame as an interim solution?

ClassOption.SHOW_IN_STACKTRACE might be one possibility.   IMO we should 
take the time and consider together with JDK-8212620 what other options 
could be explored before we provide an easy simple fix just for this 
specific case.

Mandy

On 9/7/20 11:39 AM, Uwe Schindler wrote:
> Thanks Mandy.
>
> In my opinion for the hidden classes an additional enum constant in 
> ClassOption would be fine: ClassOption.SHOW_IN_STACKTRACE (or similar).
>
> That would be simplest to implement and allows also for the caller to 
> enable it like strong references or nestmate features. So it's 
> consistent with the other API parts.
>
> The annotations are good for fine granular hiding (like complex 
> classes recursively calling methods). Or for frameworks like Spring.
>
> Should I add a comment to this issue?
>
> We are now doing some testing in Lucene's expressions module (it's 
> about scoring formulas in query execution). Here's the draft PR: 
> https://github.com/apache/lucene-solr/pull/1837/files 
> <https://urldefense.com/v3/__https://github.com/apache/lucene-solr/pull/1837/files__;!!GqivPVa7Brio!IT0c8RG8ghG1Kth5nLUmXQ-q5w0GVPR_ejFbCZB2aKzR2LJ3hXMUVgyqGK4YPZRufg$>
>
> We use the new features in Lucene when the static initializer detects 
> defineHiddenClass using a publicLookup.
>
> Currently a test fails, because of missing debug information in stack 
> traces. The executed scoring formula is part of the filename attribute 
> in class file. As this is missing, test fails. ��
>
> Uwe
>
> Am September 7, 2020 4:44:18 PM UTC schrieb Mandy Chung 
> <mandy.chung at oracle.com>:
>
>     Hi Uwe,
>
>     It's a future enhancement to allow a class/method to request
>     filtering from stack trace:
>     https://bugs.openjdk.java.net/browse/JDK-8212620
>
>     This RFE should also take hidden classes into account.
>
>     Mandy
>
>     On 9/5/20 4:55 AM, Uwe Schindler wrote:
>>     Hi,
>>
>>     I am doing a mockup for dynamically compiled scripts in Apache Lucene (later
>>     also painless scripting in elastcsearch), where I tried to use
>>     Lookup#defineHiddenClass (with default parameters, so weak and no nestmates
>>     - but: for painless scripts of Elasticsearch, nestmates will be great). It
>>     all looks great, as sometimes for every query a new class is generated.
>>
>>     The current approach (Java 8, Java 11) uses a Classloader per script, which
>>     is mostly OK, but hidden classes would be better, especially under high load
>>     with many new classes. The problem I see is: The hidden class and their
>>     methods are also hidden from stack traces, so people neither get the script
>>     source code reference, nor they get the method, which was called at all.
>>
>>     My question is: is it possible to mark such a hidden class in byte code or
>>     by a flag to defineHiddenClass() so it is "unhidden"? - I know you can do
>>     this by a command line option, but that's for developers and debugging only.
>>     In some cases, this is really wanted (like for scripting languages), but
>>     code still wants to use the better class unloading. If this is not possible,
>>     how about extending the Lookup.ClassOption enum (last parameter of
>>     defineHiddenClass), to also pass a flag to show them in stack traces?
>>
>>     Uwe
>>
>>     -----
>>     Uwe Schindler
>>     uschindler at apache.org  
>>     ASF Member, Apache Lucene PMC / Committer
>>     Bremen, Germany
>>     https://lucene.apache.org/
>>
>>
>