RFR: JDK-8232773: ClassLoading Debug Output for Specific Classes

[Adam Farley8]

Hi David,

I didn't, no. Thanks for pointing it out. :)

I see this tells us where the class comes from, much like 
"-verbose:class".

So it's useful when a class can be successfully loaded, but 
doesn't tell us which classloaders tried to load the class, 
nor where they looked, etc.

Something I could have done a better job conveying was that
the core question this debugging is meant to answer is:

"Why didn't OpenJDK load the class I wanted it to?"

"-Xlog:class+load" seems very useful for finding where a
class came from, which answers the "loading the wrong version 
of a class" problem, but does not seem to give us 
information in the case of class loading failure.

Also, thanks for moving the bug to the correct component. :)

Best Regards

Adam Farley 
IBM Runtimes


David Holmes <david.holmes at oracle.com> wrote on 22/10/2019 14:12:55:

> From: David Holmes <david.holmes at oracle.com>
> To: Adam Farley8 <adam.farley at uk.ibm.com>, Java Core Libs <core-
> libs-dev at openjdk.java.net>
> Date: 22/10/2019 14:14
> Subject: [EXTERNAL] Re: RFR: JDK-8232773: ClassLoading Debug Output 
> for Specific Classes
> 
> Hi Adam,
> 
> Did you look at the logging available from the VM: -Xlog:class+load?
> 
> BTW I moved the bug you filed to the correct component.
> 
> Cheers,
> David
> 
> On 22/10/2019 8:40 pm, Adam Farley8 wrote:
> > Hey All,
> > 
> > This one goes out to anyone who's struggled to figure out
> > why OpenJDK isn't loading their class.
> > 
> > The requirement is for OpenJDK to give more detailed
> > information while loading user-specified classes (e.g. the
> > one OpenJDK is failing to load). Some debug information is
> > available while the loading is in-progress, and more is
> > available after the fact, but it seems there is not a way
> > to monitor what the ClassLoaders are actually doing without
> > the use of debugging tools.
> > 
> > For your approval: a formal write-up of the problem (as
> > I understand it), and a draft webrev containing the
> > proposed solution.
> > 
> > Tests will be developed and added if/when the issue is
> > accepted as a problem, and a solution has been selected.
> > 
> > Please review and opine.
> > 
> > Bug: https://urldefense.proofpoint.com/v2/url?
> 
u=https-3A__bugs.openjdk.java.net_browse_JDK-2D8232773&d=DwICaQ&c=jf_iaSHvJObTbx-
> siA1ZOg&r=P5m8KWUXJf-
> 
CeVJc0hDGD9AQ2LkcXDC0PMV9ntVw5Ho&m=evj-5Q-0QflLNXj0WL5j9WrCHzNRovUvazY9IH_qNkI&s=WEfc_wG4s2o_lhOKcZOykIG0RNybBiMMVbKIzmrlY3k&e=
> > 
> > Webrev: https://urldefense.proofpoint.com/v2/url?
> 
u=http-3A__cr.openjdk.java.net_-7Eafarley_8232773_webrev_&d=DwICaQ&c=jf_iaSHvJObTbx-
> siA1ZOg&r=P5m8KWUXJf-
> 
CeVJc0hDGD9AQ2LkcXDC0PMV9ntVw5Ho&m=evj-5Q-0QflLNXj0WL5j9WrCHzNRovUvazY9IH_qNkI&s=jDSMDaCpBBZcYMU-
> IUqDh8PoCyl1Jk1G-QGIPKGjgeY&e= 
> > 
> > Thanks for your time. :)
> > 
> > Best Regards
> > 
> > Adam Farley
> > IBM Runtimes
> > 
> > 
> > Unless stated otherwise above:
> > IBM United Kingdom Limited - Registered in England and Wales with 
number
> > 741598.
> > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 
3AU
> > 
> 

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
741598. 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU