Is RegisterMap updated?

[Jini George]

Hi David,

Thank you for the explanation. From Java 9, there is the 'jhsdb' tool 
provided with the JDK, with which you can use the SA features. So, in 
this case, you can run it thus to see if you can reproduce the problem:

jhsdb jstack --core <your core file that you dumped with gcore> --exe 
<the java launcher path>

Thanks,
Jini.

On 2/2/2019 2:59 PM, David Griffiths wrote:
> Hi Jini, for that particular case, it just provides a simple way to
> reproduce more general problems in SA: first I run a program under gdb
> and with the option "-XX:CompileCommand=print,...", then I put a
> breakpoint at a particular place that I suspect the stack walker code
> has problems with. When the breakpoint hits, I do gcore in gdb and
> then have a core file to reproduce the problem with jstack or jdb
> using SACoreAttachingConnector etc. In this particular case I just
> enter the jdb "locals" command.
> 
> The more general thing that I'm doing with the SA code (not sure what
> is defined as SA and what is SA-JDI but I think the classes I use are
> still there in Java 9, just harder to access) and that I mentioned to
> Andrew once and who probably thinks I'm nuts is to use it to
> effectively debug a java application under gdb. So it's a bit like the
> attaching to a live process situation using the pid (or a core file
> for that matter). The nature of our application means that we can't
> attach to the normal JDWP agent inside the JVM - we have to use gdb
> and cannot modify the state of the running JVM. I know the code I'm
> using is a bit fuzzy and imprecise - AMD64CurrentFrameGuess is a prime
> example that I've had to improve - but fuzzy is actually enough most
> of the time.
> 
> Cheers,
> 
> David
> 
> 
> On Sat, 2 Feb 2019 at 02:51, Jini George <jini.george at oracle.com> wrote:
>>
>> Hi David,
>>
>> This got removed in JDK-9 as a part of SA-JDI removal.
>> (https://bugs.openjdk.java.net/browse/JDK-8158050). Could you let us
>> know as to why are you using SA-JDI ?
>>
>> Thanks,
>> Jini.
>>
>> On 2/1/2019 9:56 PM, David Griffiths wrote:
>>> Had a nice simple little reproduction test, went to try it on Java 9
>>> and... oh no, sun.jvm.hotspot.jdi.SACoreAttachingConnector has
>>> disappeared! Has it gone for good?
>>>
>>> Cheers,
>>>
>>> David
>>>
>>> On Wed, 30 Jan 2019 at 10:38, Andrew Haley <aph at redhat.com> wrote:
>>>>
>>>> On 1/30/19 10:00 AM, David Griffiths wrote:
>>>>> I'm not sure this works though for the frame at the top of the stack.
>>>>> The pushing of the registers that you mention appears to take place in
>>>>> the updateRegisterMap method which is called when getting the sender.
>>>>> At the top of the stack the register will be live and not saved
>>>>> anywhere?
>>>>
>>>> No the pushing of the register happens in generated code.
>>>>
>>>>> Whatever, I'm seeing a NPE caused by a location that has
>>>>> WHERE_IN_REGISTER and a register number of 16 that doesn't have
>>>>> locationValid set in the map. If I modify createStackValue to check
>>>>> valueAddr being null then it avoids the NPE and getLocals then returns
>>>>> all the locals except for the one held in a register (the other ones
>>>>> are on the stack). Not sure what a register number of 16 equates to on
>>>>> x86, is that supposed to correspond to "not set" or something?
>>>>
>>>> You're not helping.  Are you sure you've got an up-to-date HotSpot
>>>> checkout? You're not falling over bug 8217407?
>>>>
>>>> --
>>>> Andrew Haley
>>>> Java Platform Lead Engineer
>>>> Red Hat UK Ltd. <https://www.redhat.com>
>>>> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671