RFR: 8344706: Compiler Implementation of Compact Source Files and Instance Main Methods [v4]

[Jan Lahoda]

On Tue, 22 Apr 2025 08:34:36 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add clause about handling of malformed/unmappable bytes.
>
> src/java.base/share/classes/jdk/internal/misc/MethodFinder.java line 89:
> 
>> 87:         if (mainMethod == null) {
>> 88:             //if not public method, try to lookup a non-public one
>> 89:             mainMethod = JLA.findMethod(cls, false, "main", String[].class);
> 
> Is there a reason why the first findMethod can't use publicOnly=false?

My reason was that when `publicOnly=false`, there's more classloading happening (unsurprisingly, as also the non-public methods must be resolved). Which may lead to a change of behavior if the traditional `public static main(String[])` exists.

IIRC there is a test relying on this behavior, but I don't have the name offhand. Will put it here when I have it.

For example:

$ cat Main.java 
public class Main {
    public static void main(String... args) {
        System.err.println("Hello!");
    }
    private Missing get() { return null; }
}
$ cat Missing.java 
public class Missing {
}
$ jdk-24/bin/javac Main.java Missing.java; rm Missing.class
$ jdk-24/bin/java -classpath . Main
Hello!
$ jdk-without-publicOnly=true/bin/java -classpath . Main
Error: Unable to initialize main class Main
Caused by: java.lang.NoClassDefFoundError: Missing

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

PR Review Comment: https://git.openjdk.org/jdk/pull/24438#discussion_r2053808119