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

[Matthias Baesken]

On Fri, 26 May 2023 07:12:07 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> This is IBMs declaration of statfs
>> `extern int statfs(char *, struct statfs *);`
>> So the compiler will not accept a `const char*`
>> Indeed I do not know if this ever worked, but my change makes it not worse.
>
> Here is the documentation of statfs on AIX  https://www.ibm.com/docs/en/aix/7.2?topic=s-statfs-fstatfs-statfs64-fstatfs64-ustat-subroutine  (showing the IBM declaration Joachim told us) .

> Also, pre-existing, the cast seems really suspicious. The type of `chars` is `jchar*`, which is a sequence of 16bit characters. Does this actually work? If so, how?

Probably a jchar to char conversion would be needed for the array elements,  maybe like this here (or is there a better utility function in the codebase) ? See  jCharArrayToCKCharArray
https://github.com/openjdk/jdk/blob/199b1bf5009120efd1fd37a1ddabc0c6fb84f62c/src/jdk.crypto.cryptoki/share/native/libj2pkcs11/p11_util.c#L644

I am not aware of an AIX statfs for wchars but maybe I miss something.  But it is a separate issue of Java_GetXSpace_getSpace0  anyway and should be handled in another bug.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14146#discussion_r1206370114