RFR: 8354897: Support Soft/Weak Reference in AOT cache [v8]

[Ioi Lam]

On Wed, 30 Apr 2025 08:47:59 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Renamed the internal field ReferenceQueue.NULL to NULL_QUEUE to avoid failing hotspot/jtreg/sources/TestNoNULL.java
>
> src/hotspot/share/cds/aotArtifactFinder.cpp line 77:
> 
>> 75:   // into the AOT cache -- that will be decided by the code below.
>> 76:   SystemDictionaryShared::finish_exclusion_checks();
>> 77:   AOTReferenceObjSupport::init_keep_alive_objs_table();
> 
> This should be guarded with `INCLUDE_CDS_JAVA_HEAP` somehow. I guess the cleanest way would be to use `NOT_CDS_JAVA_HEAP_RETURN` in `aotReferenceObjSupport.hpp`

I added `NOT_CDS_JAVA_HEAP_RETURN` to the declaration of `init_keep_alive_objs_table`. All the other functions are called only inside `INCLUDE_CDS_JAVA_HEAP` blocks, so I didn't change them to avoid cluttering the code.

> src/hotspot/share/cds/aotReferenceObjSupport.cpp line 95:
> 
>> 93: #if INCLUDE_CDS_JAVA_HEAP
>> 94: 
>> 95: 
> 
> Suggestion:

Fixed.

> test/hotspot/jtreg/runtime/cds/appcds/aotClassLinking/WeakReferenceTest.java line 233:
> 
>> 231:         if (ref2.get() == null) {
>> 232:             throw new RuntimeException("ref2.get() should not be null");
>> 233:         }
> 
> The referent of ref2 is never strong. If a GC occurs between makeRef2() and this check, we could hit this Exception. The test should either keep it strongly reachable until after this check or just not test wether it is reachable before the call to System.gc().

I removed the check that was before the GC.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24757#discussion_r2069169854
PR Review Comment: https://git.openjdk.org/jdk/pull/24757#discussion_r2069169794
PR Review Comment: https://git.openjdk.org/jdk/pull/24757#discussion_r2069169743