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

[Kim Barrett]

On Sat, 27 May 2023 15:33:37 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> 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.

Technically it's our fault.  The standard library is permitted to provide a
macro replacements for (nearly?) any function.  (C99 7.1.3/1 3rd bullet) But
it's really annoying.  Presumably AIX is only doing so for a subset of the
allocation functions, e.g. not "free" for example.

Having "malloc" defined as a macro seems like it should raise all kinds of
havoc, not just around log tags.  Consider our "os::malloc" function?  The
preprocessor knows nothing about C++ namespace qualifiers.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14146#discussion_r1210388482