RFR: 8334031: Generated JfrNativeSettings seems off

[Robert Toyonaga]

On Wed, 26 Jun 2024 17:00:23 GMT, Erik Gahlin <egahlin at openjdk.org> wrote:

> All types in JFR is assigned an ID, regardless if they are events or a structs. If we are going to index into the array, with the event type ID, must not the holes be filled with something? Or are all native event type IDs first?

It looks like we [index using the `JfrEventId` enum](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/jfr/recorder/jfrEventSetting.inline.hpp#L30-L56). This enum [only enumerates events](https://github.com/openjdk/jdk/blob/master/make/src/classes/build/tools/jfr/GenerateJfrFiles.java#L690-L695), not all types. So I don't think there will actually be any holes. 

I'm a bit confused about why structs were included originally. It seems like it was intentional: ["_Then, to make it easy to debug, add named struct members also_"](https://github.com/openjdk/jdk/blob/master/make/src/classes/build/tools/jfr/GenerateJfrFiles.java#L667). But I can't see why it makes sense to group them with events in this way.

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PR Comment: https://git.openjdk.org/jdk/pull/19891#issuecomment-2192401387