RFR: JDK-8292914: Introduce a system property that enables stable names for lambda classes

[Strahinja Stanojevic]

On Tue, 6 Sep 2022 16:47:03 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> Have you tested with method references? Two references to the same method will result in a single `JVM_CONSTANT_InvokeDynamic` constant pool entry in the classfile, but it's invoked by two callsites. As a result, two different lambda proxy classes will be generated, as the JVMS requires the invokedynamic resolution to be per callsite, not per constantpool entry.
> 
> ```
> public class ShareBSM {
>   public static void main(String args[]) {
>     doit1(ShareBSM::func);
>     doit2(ShareBSM::func);
>   }
>   static void func() {  Thread.dumpStack();  }
>   static void doit1(Runnable r) {  r.run();  }
>   static void doit2(Runnable r) {  r.run();  }
> }
> ```
> 
> Here's the output:
> 
> ```
> $ java -cp . -XX:+UnlockDiagnosticVMOptions -XX:+ShowHiddenFrames ShareBSM
> java.lang.Exception: Stack trace
> 	at java.base/java.lang.Thread.dumpStack(Thread.java:1380)
> 	at ShareBSM.func(ShareBSM.java:8)
> 	at ShareBSM$$Lambda$1/0x0000000800c009f0.run(Unknown Source)
> 	at ShareBSM.doit1(ShareBSM.java:12)
> 	at ShareBSM.main(ShareBSM.java:3)
> java.lang.Exception: Stack trace
> 	at java.base/java.lang.Thread.dumpStack(Thread.java:1380)
> 	at ShareBSM.func(ShareBSM.java:8)
> 	at ShareBSM$$Lambda$2/0x0000000800c00bf8.run(Unknown Source)
> 	at ShareBSM.doit2(ShareBSM.java:15)
> 	at ShareBSM.main(ShareBSM.java:4)
> ```
> 
> Will you patch generate the same name for both callsites? Does this matter for your use case?

@iklam Yes, I tested it against method references too. The patch produces the same names as it should. I enhanced the test with one additional method that will explicitly use method references. We don't want confusion about this in the future.

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PR: https://git.openjdk.org/jdk/pull/10024