On Thu, 12 Mar 2026 15:36:07 GMT, Jan Lahoda <[email protected]> wrote:
> Consider these classes:
>
> package p;
> public class Lib {
> void main(String... args) {
> System.err.println("Lib!");
> }
> }
>
> and:
>
> import p.Lib;
> public class Main extends Lib {
> public void main() {
> System.err.println("Main!");
> }
> }
>
>
> Note the classes are in different packages. Running this on JDK 26 yields:
>
> $ jdk-26/bin/java Main.java
> Lib!
>
>
> that is not correct - the method `Lib.main(String[])` is package private, and
> is not inherited to `Main`, i.e. not a member of `Main`, and hence the
> launcher should not use it. The launcher should only inspect methods that are
> members (direct or inherited) of `Main`.
>
> This PR fixes that by only using package-private methods in they are declared
> in the same class as is the main class. Testing is enhanced to cover all
> related cases I/we were able to find.
>
> Also please review the corresponding CSR:
> https://bugs.openjdk.org/browse/JDK-8378555
src/java.base/share/classes/jdk/internal/misc/MethodFinder.java line 107:
> 105: (Modifier.isPublic(mainMethodCandidate.getModifiers()) ||
> 106: Modifier.isProtected(mainMethodCandidate.getModifiers())
> ||
> 107: initialClass.getPackage() ==
> mainMethodCandidate.getDeclaringClass().getPackage());
Hello Jan, `Class.getPackage()` doesn't specify that it will return the same
`Package` instance for multiple calls of that method on the same `Class`
instance. Briefly looking at the implementation, it appears that only
`BootClassLoader` might return the same `Package` instance for multiple calls.
I was going to suggest that maybe we should use `Package.equals()`, but I can't
find an implementation of that method in `Package`, so it would again end up
being a identity check.
The other option would be checking the package name `equals()`ity but I think
that would also additionally need a ClassLoader equality check for
`initialClass.getClassLoader()` and
`mainMethodCandidate.getDeclaringClass().getClassLoader()`
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/30221#discussion_r2960427344
