RFR: 8342860: Fix more NULL usage backsliding [v2]

[Kim Barrett]

On Tue, 5 Nov 2024 15:05:51 GMT, theoweidmannoracle <duke at openjdk.org> wrote:

>> - Changed several "NULL" in comments to "null"
>> - Changed several `NULL` in code to `nullptr`
>
> theoweidmannoracle has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8342860
>  - Fix copyright year
>  - 8342860: Fix more NULL usage backsliding

Can you use the (updated) regex in the JBS issue description to verify the only
remaining "NULL"s in src/hotspot are jvmti.{xml,xsl} and
globalDefinitons_{gcc,visCPP}.hpp?

There are also some new NULLs in test/hotspot.
./jtreg/serviceability/jvmti/GetMethodDeclaringClass/libTestUnloadedClass.cpp
./jtreg/serviceability/jvmti/vthread/VThreadEventTest/libVThreadEventTest.cpp
There are a couple more (after filtering out java and C source files) that I think
shouldn't be changed.

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Changes requested by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21826#pullrequestreview-2415914752