RFR: 8315130: java.lang.IllegalAccessError when processing classlist to create CDS archive [v10]

[Calvin Cheung]

On Wed, 16 Apr 2025 14:34:25 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> If a base class is package-private then its subclasses should have the same package name and defining class loader, otherwise `IllegalAccessError` is thrown when linking a subclass. Currently when dumping a static archive separate `URLClassLoader`s are used for each unregistered classes' source. Thus if two unregistered classes, a package-private base class and a sub class, from the same package reside in different sources `IllegalAccessError` will be thrown when linking the sub class. This can be unexpected because the app could have used a single class loader for both classes and thus not have seen the error — see `DifferentSourcesApp.java` from this patch for an example of such app.
>> 
>> This patch fixes the issue by using a single class loader for all unregistered classes. CDS does not allow classes with the same name making such solution possible.
>
> Timofei Pushkin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 15 commits:
> 
>  - Empty commit to make GH update the PR
>  - Merge remote-tracking branch 'openjdk-jdk/master' into one-loader
>  - Implement super overshadowing warning
>  - Omit Source classes from archive
>  - Remove unused imports
>  - Fix indentation
>  - Extend ClassFromClasspath test
>  - Remove findClass, extend explanation comments
>  - Remove unnecessary scoping
>  - Don't use URLClassPath
>  - ... and 5 more: https://git.openjdk.org/jdk/compare/465c8e65...595756f3

Found an issue on the RegUnregSuperTest.java.

test/hotspot/jtreg/runtime/cds/appcds/customLoader/RegUnregSuperTest.java line 77:

> 75:             out.shouldContain("CustomLoadee3Child (id 3) has super-type CustomLoadee3 (id 1) overshadowed by another class with the same name");
> 76:         } else {
> 77:             out.shouldContain("unreg CustomLoadee3Child\n");

Could you remove the linefeed ('\n') chars?
I'm seeing test failure when running with the `-XX:+AOTClassLinking` option.


java.lang.RuntimeException: 'app   CustomLoadee3
' missing from stdout/stderr
	at jdk.test.lib.process.OutputAnalyzer.shouldContain(OutputAnalyzer.java:253)
	at RegUnregSuperTest.main(RegUnregSuperTest.java:71)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
	at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:335)
	at java.base/java.lang.Thread.run(Thread.java:1447)

The expected output is there:
`[1.686s][debug  ][cds,class] klasses[ 1548] = 0x00000008004c7518 app   CustomLoadee3 aot-linked`

-------------

Changes requested by ccheung (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/24223#pullrequestreview-2774638133
PR Review Comment: https://git.openjdk.org/jdk/pull/24223#discussion_r2048272791