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 the jvmti.{xml,xls} files and the
globalDefinitions_{gcc,visCPP}.hpp files?

There are also some NULLs recently introduced in test/hotspot:
./jtreg/serviceability/jvmti/GetMethodDeclaringClass/libTestUnloadedClass.cpp
./jtreg/serviceability/jvmti/vthread/VThreadEventTest/libVThreadEventTest.cpp

(Found by applying the same regex to test/hotspot, and then removing .java and
.c files.)

There are a few other files in test/hotspot containing NULLs:
./jtreg/vmTestbase/nsk/share/jni/README
./jtreg/vmTestbase/nsk/share/jvmti/README
These are documentation files with examples written in C, so should not be changed.

./jtreg/vmTestbase/nsk/share/native/nsk_tools.hpp
In a comment describing a string to be used for printing.  Uses would need to
be examined to ensure it's okay to change the string used for a null value.
I think I planned to do this as a followup to JDK-8324799, and then forgot.
I'd be okay with doing something about this being separate from the current
PR.  While the necessary textual changes are probably small, there's a lot of
uses to examine to be sure a change is okay.

-------------

Changes requested by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21826#pullrequestreview-2416066994