Invalid code generated by C2 compiler in OpenJDK 21

[David Holmes]

I will need to follow up on this tomorrow. Even with the mistake I 
cannot see how it can possibly lead to the NPE.

Thanks,
David

On 18/12/2023 10:07 pm, Antoine DESSAIGNE wrote:
> Quick follow-up, Aleksey Shipilev created the bug [1] and the pull
> request [2] as I have no idea how long it will take for me to have the
> signed OCA :)
> 
> Thank you all
> 
> Antoine
> 
> [1] https://bugs.openjdk.org/browse/JDK-8322282
> [2] https://github.com/openjdk/jdk/pull/17140
> 
> Le lun. 18 déc. 2023 à 12:41, Antoine DESSAIGNE
> <antoine.dessaigne at gmail.com> a écrit :
>>
>> Hello everyone,
>>
>> Good news, I've found the typo in
>> https://github.com/openjdk/jdk/commit/10737e168c967a08e257927251861bf2c14795ab,
>> it's in loaderConstraints.cpp.
>>
>> Previously it was
>>    } else if (pp1 == NULL) {
>>      pp2->extend_loader_constraint(class_name, class_loader1, klass);
>>    } else if (pp2 == NULL) {
>>      pp1->extend_loader_constraint(class_name, class_loader2, klass);
>>
>> Now it is (and still is on master but line numbers have changed)
>>    } else if (pp1 == NULL) {
>>      pp2->extend_loader_constraint(class_name, loader1, klass);
>>    } else if (pp2 == NULL) {
>>      pp1->extend_loader_constraint(class_name, loader1, klass);
>>
>> The last line should be using loader2
>>      pp1->extend_loader_constraint(class_name, loader2, klass);
>>
>> If I do the fix locally then I no longer have the issue.
>>
>> Now, I don't know what to do next to have it fixed. Can someone either
>> do it or tell me how to do it? Thank you.
>>
>> Le lun. 18 déc. 2023 à 12:04, Andrew Haley
>> <aph-open at littlepinkcloud.com> a écrit :
>>>
>>> On 12/18/23 10:08, Antoine DESSAIGNE wrote:
>>>
>>>   >
>>>   > Once the reference to Interval is copied into my local variable
>>>   > storedValueVT, no change on the other class can change it.
>>>
>>> I'm not sure about that. C2 contains logic to rematerialize a value
>>> rather than spilling, if it's cheaper. That could be happening here.
>>> At least, I know of no place in the JMM that forbids it.
>>>
>>> As an experiment, you could try making validTime volatile.
>>>
>>> --
>>> Andrew Haley  (he/him)
>>> Java Platform Lead Engineer
>>> Red Hat UK Ltd. <https://www.redhat.com>
>>> https://keybase.io/andrewhaley
>>> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
>>>