On Thu, 19 Mar 2026 14:34:04 GMT, Jaikiran Pai <[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 102:
>
>> 100: }
>> 101:
>> 102: private static boolean isValidMainMethod(Class<?> initialClass,
>> Method mainMethodCandidate) {
>
> The `mainMethodCandidate` that gets passed here is sourced from a call to
> `JavaLangAccess.findMethod(...)`. As far as I can see, the implementation of
> that `findMethod()` could return an `abstract` or `native` method named
> `main(...)`. Should additional checks be added here in `isValidMainMethod()`
> to skip such methods?
>
> Of course, this isn't due the change you have done here and it's pre-existing
> code. So it brings up the question whether we currently don't have tests to
> verify that such unexpected main methods don't get prefered in this
> implementation (and then fail to launch).
I just gave this a try against Java 26:
public class BaseClass {
public void main() {
System.out.println("hello from " + BaseClass.class);
}
}
public class ChildClass extends BaseClass {
public native void main();
}
Then compiled them:
javac BaseClass.java ChildClass.java
and launched the `ChildClass`:
java ChildClass
This fails with:
Exception in thread "main" java.lang.UnsatisfiedLinkError: 'void
ChildClass.main()'
at ChildClass.main(Native Method)
which I think is wrong, and instead the `java` launcher should have picked up
`BaseClass.main()` as the main entry point?
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/30221#discussion_r2960551439
