RFR: 8166187: Regression: NPE during reparse when using persistent code cache and optimistic types

[Hannes Wallnöfer]

Thanks Attila, I had forgotten cached AST is not just a performance feature.

I uploaded a new webrev. It pretty much follows your suggestions, except I used a slightly different approach to conditional serialization of cachedAst - I left the field transient and serialize it explicitly if it is an instance of SerializedAst, otherwise write out null. I also added a test case for split stored functions.

http://cr.openjdk.java.net/~hannesw/8170977/webrev.01/ 

Hannes


> Am 22.12.2016 um 16:48 schrieb Attila Szegedi <szegedia at gmail.com>:
> 
> Hm… cachedAst is essential for split functions; specifically if it contains a SerializedAst, then its "byte[] serializedAst" field is essential. If cachedAst is lost, we can reparse an unsplit function from source, but we can’t reparse fragments of split functions.
> 
> I’d suggest instead of making cachedAst transient, we should:
> 1. make SerializedAst Serializable, and have SerializedAst.cachedAst within it transient (reference objects aren’t serializable, and we can afford to lose it anyway).
> 2. introduce RecompilableScriptFunctionData.writeObject and make sure that if serializedAst contains a reference (instead of a SerializedAst object) then we don’t attempt to serialize it — write null instead (this can be accomplished by just setting serializedAst = null, and maybe re-setting it back to what it was after defaultWriteObject)
> 3. make sure there’s a null check on SerializedAst.cachedAst read in getCachedAst() (as now it can actually be null on deserialization, it was an invariant that it was never null before)
> 
> Attila.
> 
>> On 22 Dec 2016, at 16:18, Hannes Wallnöfer <hannes.wallnoefer at oracle.com> wrote:
>> 
>> Please review: 
>> 
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8166187
>> Webrev: http://cr.openjdk.java.net/~hannesw/8166187/webrev/
>> 
>> It was actually the combination of having a non-serialisable AST reference and not initialising the transient fields of nested functions that caused this error.
>> 
>> Thanks,
>> Hannes
>