RFR: 8336382: Fix error reporting in loading AWT [v10]

[Karm Michal Babacek]

On Wed, 29 Jan 2025 23:33:18 GMT, Karm Michal Babacek <duke at openjdk.org> wrote:

>> So this is much better than what was there in the beginning.
>> FindClass failing - for a key API class - is probably a fatal error one way or another.
>> Although in all (?) other cases, we try to return to Java and let the VM throw a Java-level error.
>> Note that OnLoad is not the only code path that calls AWTIsHeadless, and there will be
>> Java code to return to in the other case.
>> However I think that the OnLoad will always be reached first, so maybe it is OK to do the current fix.
>> Either way, things aren't going to work.
>> 
>> Generally the calls to check and clear exceptions when looking up code are there
>> to keep 'tools' happy. If these classes aren't found something is badly wrong.
>> meaning it should NEVER EVER happen.
>> Failing to find java/lang/String for example hardly seems like something it is worth trying to recover from ..
>> In your case it seems like it does some times happen for GraphicsEnvironment which still worries me.
>> I don't want to make this fix a precedent for assuming that it is normal for classes to be missing.
>> So consider it a truly exceptional case.
>
>> So this is much better than what was there in the beginning. FindClass failing - for a key API class - is probably a fatal error one way or another. Although in all (?) other cases, we try to return to Java and let the VM throw a Java-level error. Note that OnLoad is not the only code path that calls AWTIsHeadless, and there will be Java code to return to in the other case. However I think that the OnLoad will always be reached first, so maybe it is OK to do the current fix. Either way, things aren't going to work.
>> 
>> Generally the calls to check and clear exceptions when looking up code are there to keep 'tools' happy. If these classes aren't found something is badly wrong. meaning it should NEVER EVER happen. Failing to find java/lang/String for example hardly seems like something it is worth trying to recover from .. In your case it seems like it does some times happen for GraphicsEnvironment which still worries me. I don't want to make this fix a precedent for assuming that it is normal for classes to be missing. So consider it a truly exceptional case.
> 
> Thank you for the review. This is indeed an awkward, yet real-world exceptional case.

> @Karm I've updated the subject of the JBS issue; please update the PR subject.

Thank you @aivanov-jdk . Done.

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PR Comment: https://git.openjdk.org/jdk/pull/20169#issuecomment-2623169473