RFR: JDK-8308288: Fix xlc17 clang warnings in shared code [v2]

[Martin Doerr]

On Fri, 26 May 2023 08:31:46 GMT, JoKern65 <duke at openjdk.org> wrote:

>> When using the new xlc17 compiler (based on a recent clang) to build OpenJDk on AIX , we run into various "warnings as errors".
>> Some of those are in shared codebase and could be addressed by small adjustments.
>> A lot of those changes are in hotspot, some might be somewhere else in the OpenJDK C/C++ code.
>
> JoKern65 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   forgotton _

Just a side note: The warning elimination is new for AIX compilers. We had given it up at earlier times: https://bugs.openjdk.org/browse/JDK-8202325
I still appreciate if we can get warning free and it makes sense to review all of them. But, I wouldn't require it for JDK21.

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PR Comment: https://git.openjdk.org/jdk/pull/14146#issuecomment-1564406986