RFR: 8267118: OutOfMemoryError cannot be caught as a Throwable [v2]

[Coleen Phillimore]

On Mon, 31 May 2021 06:39:49 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 two additional commits since the last revision:
> 
>  - Merge branch 'master' into 8267118-oome
>  - 8267118: OutOfMemoryError cannot be caught as a Throwable

This seems reasonable to me.

src/hotspot/share/oops/method.cpp line 232:

> 230:   if (do_logging) {
> 231:     ResourceMark rm(THREAD);
> 232:     log_info(exceptions)("Looking for catch handler for exception of type \"%s\" in method \"%s\"",

I think these should be log_debug, since this is useful for debugging but many people outside of hotspot engineers use -Xlog:exceptions.

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Changes requested by coleenp (Reviewer).

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