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

[David Holmes]

On 28/02/2017 11:14 AM, Ioi Lam wrote:
> Now sure if this has been suggested before -- how about including the
> BCI in the exception message. That will tell you exactly where the
> exception happened. In fact we can do this for any exception, not just
> NPEs. Like:

One of the bug reports references BCIs. Not sure how useful that is to 
the end developer though as they typically want to map an exception to a 
place in the source code.

Cheers,
David

>
> try {
>     someThingSecure().someThingElseSecure().evenMoreSecure();
> } catch (Security Exception e) {
>     e.printStackTrace();
> }
>
> - Ioi
>
> On 2/27/17 4:45 AM, David Holmes 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
>>>
>