RFR: 8339120: Use more fine-granular gcc unused warnings [v6]

[Julian Waters]

On Wed, 28 Aug 2024 15:17:52 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> Currently, we issue -Wno-unused for all files in gcc, which is a rather big sledgehammer to get rid of some warnings that proliferate in a few areas of the build.
>> 
>> We should instead leave -Wunused turned on (as done by -Wall) and use a much more fine-grained approach to disabling specific warnings in specific files or libraries.
>
> Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Roll back indentation fix

Marked as reviewed by jwaters (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/20733#pullrequestreview-2266632564