#ReflectiveAccessByInstrumentationAgents

[Andrew Dinn]

On 20/04/16 12:40, Alan Bateman wrote:
> 
> On 19/04/2016 18:00, Andrew Dinn wrote:
>> :
>> I have been building and testing on JDK9 Byteman using the EA program
>> releases and have not seen anything break so far. However, that may just
>> be because i) Byteman and the Byteman tests are only using runtime
>> classes from the java base module and ii) app code used in tests is not
>> modularized -- well, at least not using Jigsaw (see below).
> It's good to hear that you are testing with the EA builds.
> 
> I think the main thing for Byteman, and this will be true at least some
> other agents too, is that there will likely need to be updated to
> support instrumentation with modules. We have a reasonable compatibility
> story for existing JVM TI and java agents but as soon as you get into
> instrumenting code to statically or reflectively access code in other
> modules then it may require the agent to arrange for this access to be
> allowed.

Having to explicitly manage module dependencies to retain compatibiity
with previous behaviour is at the very least a /nuisance/ because it now
means I -- and, no doubt, others in the agent business -- will have to
implement a dual-source agent, one for JDK9(+) and another to continue
to operate in JDK8/7/6 (yes, people can and do still use the latest
Byteman release in all those JDK releases). A solution internal to the
JVM which preserved existing behaviour and so did not require the
insertion of JDK-specific jumps through JDK-specific hoops would be much
preferred. Still, I suppose the releavant implementors are a relatively
small crowd and ought to know what we are doing and how to fix it.

That minor rant aside (sorry, I feel better for that but I don't suppose
anyone else on this list does :-) I will happily investigate the
available dynamic module-management APIs and see what options exist to
remedy the changes to the status quo and retain as much backwards
compatibility as I can. At that point I will come back and comment on
the very useful advice you have provided below. Thanks very much for
your help so far.

regards,


Andrew Dinn
-----------
Senior Principal Software Engineer
Red Hat UK Ltd
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