RFR: 8278021: Fix warnings in macOS glass native code and treat warnings as errors [v4]

[Martin Fox]

On Fri, 2 Feb 2024 22:17:15 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> No, we're not. The `@available` generates a runtime check so that code is executed only if the runtime platform is macOS 14.x or later.

Right, forgot about the other `@available` check.

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PR Comment: https://git.openjdk.org/jfx/pull/687#issuecomment-1924791132