RFR: JDK-8324682 Remove redefinition of NULL for XLC compiler [v3]

[Joachim Kern]

On Mon, 4 Mar 2024 09:06:03 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

>> Remove redefinition of NULL for XLC compiler
>> In globalDefinitions_xlc.hpp there is a redefinition of NULL to work around an issue with one of the AIX headers (<dirent.h>). 
>> Once all uses of NULL in HotSpot have been replaced with nullptr, there is no longer any need for this, and it can be removed.
>> 
>> 
>> JBS ISSUE : [JDK-8324682](https://bugs.openjdk.org/browse/JDK-8324682)
>
> Suchismith Roy has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   remove AIX check for NULL

Changes requested by jkern (Author).

src/hotspot/share/utilities/globalDefinitions.cpp line 160:

> 158:   static_assert((size_t)HeapWordSize >= sizeof(juint),
> 159:                 "HeapWord should be at least as large as juint");
> 160:   static_assert(sizeof(nullptr) == sizeof(char*), "NULL must be same size as pointer");

After this change that line makes no sense anymore. If there is no NULL in the complete code you can remove the line. If there are still some NULL than you have to keep the previous state.

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PR Review: https://git.openjdk.org/jdk/pull/18064#pullrequestreview-1919279460
PR Review Comment: https://git.openjdk.org/jdk/pull/18064#discussion_r1514171126