RFR: 8267118: OutOfMemoryError cannot be caught as a Throwable [v5]

[David Holmes]

On 2/06/2021 4:40 pm, Ioi Lam wrote:
> On Tue, 1 Jun 2021 23:39:07 GMT, David Holmes <dholmes at openjdk.org> wrote:
> 
>>> This interesting little quirk was discovered by @iklam. During verification, the catch-type in a catch clause is normally resolved as part of being checked to see that it is a subclass of Throwable. At runtime when an exception is thrown, we also have to check if the exception being thrown is assignable to the catch-type and so handled by that catch block. For the case where the catch-type is Throwable itself, the verification subclass check trivially passes (due to a name match) without actually resolving the CP entry for the catch-type. So at runtime when the exception is thrown we have to perform the CP resolution of the catch-type. But the resolution process itself can trigger exceptions and in particular if we have thrown OutOfMemoryError, the resolution may throw a secondary OutOfMemoryError, which prevents the first from being caught by the catch block!
>>>
>>> The fix is to force resolution of the catch-type at verification time, when it is Throwable.
>>>
>>> To aid in debugging the original problem I've also added some new logging statements that show how we find a catch block and if we encounter further exceptions in trying to catch the exception - see example in the JBS issue.
>>>
>>> Testing: tiers 1-3, plus the new test
>>>
>>> Thanks,
>>> David
>>
>> David Holmes has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:
>>
>>   - Merge branch 'master' into 8267118-oome
>>   - Simplified logging to reuse Info statements as suggested by @coleenp
>>   - Fix mh() usage
>>   - Reworked the new logging to seperate Info and Debug levels to reduce verbosity, per
>>     feedback from @coleenp @iklam
>>   - Merge branch 'master' into 8267118-oome
>>   - 8267118: OutOfMemoryError cannot be caught as a Throwable
> 
> Latest version LGTM.

Thanks Ioi!

David
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> PR: https://git.openjdk.java.net/jdk/pull/4266
>