RFR: JDK-8306304: Fix xlc17 clang warnings in ppc and aix code [v2]

[JoKern65]

On Fri, 12 May 2023 21:59:11 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> JoKern65 has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   cosmetic changes
>
> src/hotspot/os/aix/os_aix.cpp line 464:
> 
>> 462:       guarantee0(shmid != -1); // Should always work.
>> 463:       // Try to set pagesize.
>> 464:       struct shmid_ds shm_buf = { {0,0,0,0,0,0,0,0},0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
> 
> Would just `= {};` work?  (I think it should, but with warnings who knows...)

os_aix.cpp:460:37: error: missing field 'gid' initializer [-Werror,-Wmissing-field-initializers]
      struct shmid_ds shm_buf = { 0 };

={} seems to work, but I do not know if it works on every compiler because standard says: the initializer must be a **non-empty, (until C23)** brace-enclosed, comma-separated list of initializers for the members.
Should I then disable Warning missing-field-initializers?

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PR Review Comment: https://git.openjdk.org/jdk/pull/13953#discussion_r1193583982