Non urgent question on https://bugs.openjdk.java.net/browse/JDK-4834738 (Adding which Object is null to an NPE)

[Martijn Verburg]

Hi David,

Thanks for the explanation, much appreciated!

Cheers,
Martijn

On 27 February 2017 at 12:45, David Holmes <david.holmes at oracle.com> wrote:

> Hi Martijn,
>
> On 27/02/2017 10:03 PM, Martijn Verburg wrote:
>
>> Hi all,
>>
>> The topic of adding more useful information to an NPE came up on the Java
>> Champions list and after some digging we discovered some implementations
>> elsewhere (SAP VM for example) and some historical conversations / issues.
>>
>> https://bugs.openjdk.java.net/browse/JDK-4834738
>> http://mail.openjdk.java.net/pipermail/hotspot-dev/2014-April/013535.html
>>
>
> As I state in that linked topic that request was almost the inverse of
> other requests in this area - it wanted to report the method invoked on the
> null reference, whereas other requests were seeking more information on
> where the null arose eg in:
>
> a().b().c();
>
> which invocation produced the NPE. But thinking about it again, perhaps
> reporting the member access that triggered the NPE is the most generally
> useful information to provide.
>
> The bug is listed as won't fix but didn't have any explanation added to it
>> as to why.  Is it just a case that the JIT and/or other mechanisms strips
>> away that sort of information at runtime?
>>
>
> The bug was closed as "won't fix" as part of a general cleanup up of old
> issues for which there are no active plans to address the issue.
>
> As I've commented in some of the issues where this was raised (and they
> are all quite old) there is a general lack of context available to give a
> meaningful error message about the NPE.
>
> Cheers,
> David
>
> Cheers,
>> Martijn
>>
>>