RFR: 8377712: ConstantPool of WeakReferenceKey is not deterministic in CDS archive

[Ioi Lam]

On Wed, 11 Feb 2026 20:28:15 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> We are seeing intermittent failures (12 times in Jan 2026) where the CDS archives generated in the JDK build is not deterministic.
> 
> The symptom is that (perhaps due to the peculiarity of hash codes and memory addressing??) the constant pool entry for `ReferenceKey<?>` in the `WeakReferenceKey` class is not resolved when the failure happens.
> 
> The fix is for the JVM to call a method in `WeakReferenceKey` to force this entry to be resolved.

> I think a better approach might be in ReferencedKeyMap.prepareForAOTCache, after
> 
> ```
>         for (ReferenceKey<K> key : map.keySet()) {
>             Object referent = key.get();
> ```
> 
> inject a call `key.equals(new StrongReferenceKey(referent))`, so that we hit the instanceof. What do you think? This code should be less reliant to weird translation hacks and requires less VM hacks.

> A better approach might be as simple as calling `MethodType.methodType()` to retrieve an existing method type, maybe `MethodType.methodType(void.class)` would be sufficient, in `MethodType::assemblySetup`.

`ReferencedKeyMap.prepareForAOTCache()` is only called only when `AOTClassLinking` is true. However, when creating the default CDS archives, `AOTClassLinking` is false.

Also, I am not sure if we should insert unnecessary code to try to achieve some unobvious side effect.

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PR Comment: https://git.openjdk.org/jdk/pull/29678#issuecomment-3888436219