[foreign-jextract] RFR: 8249949: jextract libclang Cursor children iteration creates a new up call stub every time

[Maurizio Cimadamore]

On Thu, 23 Jul 2020 07:53:19 GMT, Athijegannathan Sundararajan <sundar at openjdk.org> wrote:

> Avoiding repeated upcall stub creation by caching. The array list updated is updated in a synchroinzed method.

src/jdk.incubator.jextract/share/classes/jdk/internal/clang/Cursor.java line 338:

> 337:
> 338:     private static class CursorChildren {
> 339:         private static final ArrayList<Cursor> children = new ArrayList<>();

Wrapping the logic in a class is a good idea, but I think we can go further and avoid reusing the same static. E.g. we
could make the list an _instance_ field, and then the static `get` method would create a new instance of
`CursorChildren` (to do the visit) and then return the list attached to that instance.

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PR: https://git.openjdk.java.net/panama-foreign/pull/261