Accessing module internals from bytecode rewriting agent

Kirk Pepperdine kirk.pepperdine at
Fri May 5 06:44:34 UTC 2017

Hi Jeremy,

I think your email points out *why* turning this on out of the blocks is going to make things a ton more difficult. IMHO, 9 needs to be opt-in rather than opt-out. By 10 I think we’ll be ready for opt-out rather than opt-in.

Kind regards,
Kirk Pepperdine

> On May 5, 2017, at 8:39 AM, Jeremy Manson <jeremymanson at> wrote:
> Thanks, Dalibor.
> I know it may sound surprising, but I'm not actually complaining.  I do
> understand that most everything we're doing that requires workarounds for
> modules is unsupported (with the possible exception of the changes to
> instrumentation agents), and we were always doing them at our own risk.
> This is far from limited to Xbootclasspath - we have all sorts of hacks,
> including, to pick two things at random among many, code that introspects a
> Thread's Runnable to pick a good name to report for a thread, and code that
> introspects an AbstractInterruptibleChannel to stop the owning thread from
> closing the channel when it gets an interrupt.
> It's our problem to fix these issues, and I'm unlikely to claim otherwise.
> Frankly, it doesn't seem all that difficult to find other ways to
> introspect into the JDK - it's just busywork and more awkward than it used
> to be.
> Mostly, I'm telling you all because I think it makes an interesting case
> study - a large Java installation and the issues it faces trying to roll
> out JDK 9.
> If other installations do the kinds of things that we do, the path to a JDK
> 9 without lots of add-exports and kill switch options is likely to be slow
> and laborious for them.  We're comparatively well situated to do it - we
> have our own JDK build and a staffed team to do / help with the migration,
> and are likely to roll it out to everyone with the kill switch turned on by
> default so that our awful hacks can stay put until we finish fixing them.
> (Also, if I were complaining, there would have been a lot of choice things
> I would have said that I'm not going to say. :) )
> Jeremy
> On Thu, May 4, 2017 at 4:35 AM, dalibor topic <dalibor.topic at>
> wrote:
>> On 02.05.2017 18:46, Jeremy Manson wrote:
>>> People
>>> are using Xbootclasspath for a variety of things.
>> It's worth keeping in mind when using such options that
>> "Non-standard options are general purpose options that are specific to the
>> Java HotSpot Virtual Machine, so they are not guaranteed to be supported by
>> all JVM implementations, and are subject to change. These options start
>> with -X."
>> va.html#BABHDABI
>> cheers,
>> dalibor topic
>> --
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