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

[Kim Barrett]

On Sat, 27 May 2023 11:50:11 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>>> This one is not just to get rid of a warning. We get real test errors because malloc gets replaced by vec_malloc in log tags.
>> 
>> That does not invalidate my argument, nor does it answer my question. Those test errors could be also fixed by renaming the log tag. Maybe that would be the better way. 
>> 
>> Also, I'm curious, why does it not complain about "free", which is a logtag as well?
>
> I am basically worried that undefining malloc, even if it seems harmless now, exposes us to difficult-to-investigate problems down the road, since it depends on how the libc devs will reform those macros in the future. I would prefer a simple solution that does not depend on how the libc includes evolve.

Is it possible to see the stdlib.h source code that is being a problem?  Maybe more eyes can come up
with a better solution, or at least come to a better understanding of why we have to go this way.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14146#discussion_r1208039639