Hi Coleen, thanks for looking into this. My original mail was the following:
Hello everybody, classes that are loaded via Unsafe::defineAnonymousClass are not transformed by a registered ClassFileTransformer. At the same time, it is possible to retransform / redefine such an anonymous classes using the instrumentation API. Here is a rather confusing bug that I encountered when working with an internally used Java agent after upgrading a code base to Java 8: The Java agent attaches at runtime (agentmain). It then registers a ClassFileTransformer that also applies for retransformation. Afterwards, all loaded classes that fullfil a given condition are explicitly registered to be retransformed by the agent. (Doing so, anonymous classes are returned by Instrumentation::getAllLoadedClasses.) This resulted in the following behavior of the agent: a) If the agent was attached after an anonymous class was loaded, the retransformation would apply to an anonymous class. b) If the agent was attached "too early", the (non-re-)transformation would not apply to an anonymous class. I wonder if it is intentional that a ClassFileTransformer is not applied when an anonymous class is loaded. Personally, I find this counter-intuitive, especially when converting anonymous inner classes to lambda expressions where many users of instrumentation do not forsee the behavioral change. It also puts a very unforseeable limit to the instrumentation API. I would therefore like to suggest that ClassFileTransformers are also applied to anonymous classes when Unsafe::defineAnonymousClass is called just as when going via ClassLoader::defineClass. I can tell that this behavior has not only affected me as I had this question comming up by multiple users of my open-source code generation library. What is your view on this? Thank you for your feedback! Best regards, Rafael 2016-01-22 15:00 GMT+01:00 Coleen Phillimore <coleen.phillim...@oracle.com>: > > > On 1/22/16 4:11 AM, Andrew Dinn wrote: >> >> On 21/01/16 22:14, Rafael Winterhalter wrote: >>> >>> Hi Andrew, >>> if there is any update on the matter, I would of course love to hear >>> about it. >>> Unfortunately, I never received an answer to my question, but maybe I >>> picked the wrong list. >>> Thank you for your support on this issue! >> >> I'm pretty sure this is the right list. But I don't know who cold answer >> the question. I know that Coleen Phillmore (added explicitly to CC) >> often deals with ClassFileTransformer issues. Coleen, can you answer? > > > Can you send the question again? I didn't see it. I also mostly look at > JVM code and rarely deal with the Java side. > > I'm also adding Dan, Serguei and Markus. > > Thanks, > Coleen > >> >> regards, >> >> >> Andrew Dinn >> ----------- >> Senior Principal Software Engineer >> Red Hat UK Ltd >> Registered in UK and Wales under Company Registration No. 3798903 >> Directors: Michael Cunningham (US), Michael O'Neill (Ireland), Paul >> Argiry (US) > >
