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

[David Holmes]

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
>