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

[Ioi Lam]

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

src/hotspot/share/cds/classListParser.cpp line 517:

> 515:     return;
> 516:   }
> 517:   assert(!supertype->is_shared_unregistered_class(), "unregistered supertype cannot be overshadowed");

Does this always prevent an unregistered class to use any other unregistered class as its super type?

I think a better check would be here:


    if (!k->local_interfaces()->contains(specified_interface)) {
+     jio_fprintf(defaultStream::error_stream(), "Specified interface %s (id %d) is not directly implemented\n",
+           specified_interface->external_name(), _interfaces->at(i));
      print_specified_interfaces();
      print_actual_interfaces(k);
+     throw exception .....      
-     error("Specified interface %s (id %d) is not directly implemented",
-           specified_interface->external_name(), _interfaces->at(i));
      }

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

PR Review Comment: https://git.openjdk.org/jdk/pull/24223#discussion_r2047820496