8336346: Fix -Wzero-as-null-pointer-constant warnings in jvmciJavaClasses.cpp

[kimbarrett]

Please review this trivial change to remove -Wzero-as-null-pointer-constant
warnings (when enabled), triggered by assignment to or comparison with a
jfieldID (a pointer type) with a value of 0. Changing the value to nullptr
removes the warnings.

Because these changes are in macros that are used many times, this change
removes about 100 warnings.

Testing: mach5 tier1

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8336346: Fix -Wzero-as-null-pointer-constant warnings in jvmciJavaClasses.cpp (Enhancement - P4)

Reviewers

• Julian Waters (@TheShermanTanker - Committer)
• Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/20175/head:pull/20175
$ git checkout pull/20175

Update a local copy of the PR:
$ git checkout pull/20175
$ git pull https://git.openjdk.org/jdk.git pull/20175/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 20175

View PR using the GUI difftool:
$ git pr show -t 20175

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/20175.diff

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[bridgekeeper]

👋 Welcome back kbarrett! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@kimbarrett This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8336346: Fix -Wzero-as-null-pointer-constant warnings in jvmciJavaClasses.cpp

Reviewed-by: jwaters, thartmann

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 61 new commits pushed to the master branch:

• 35df48e: 8335860: compiler/vectorization/TestFloat16VectorConvChain.java fails with non-standard AVX/SSE settings
• 7bf5313: 8335480: Only deoptimize threads if needed when closing shared arena
• 1b83bd9: 8336661: Parallel: Remove stacks_empty assert in PSScavenge::invoke
• 72297d2: 8317720: RISC-V: Implement Adler32 intrinsic
• 21a6cf8: 8336587: failure_handler lldb command times out on macosx-aarch64 core file
• 78cc0f9: 8336091: Fix HTML warnings in the generated HTML files
• bcb5e69: 8335921: Fix HotSpot VM build without JVMTI
• 10186ff: 8336300: DateFormatSymbols#getInstanceRef returns non-cached instance
• 7ec55df: 8336638: Parallel: Remove redundant mangle in PSScavenge::invoke
• 6df7acb: 8299080: Wrong default value of snippet lang attribute
• ... and 51 more: https://git.openjdk.org/jdk/compare/9b6f6c5c9dd6d0fbb056e8d84c3a0888a3320edf...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[openjdk]

@kimbarrett The following labels will be automatically applied to this pull request:

• graal
• hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 01: Full - Incremental (d5b51135)
• 00: Full (c6734072)

[TheShermanTanker]

Alignment of the backslash seems off

[kimbarrett]

Fixed.

[TobiHartmann]

Looks good to me too.

[kimbarrett]

Thanks for reviews @TheShermanTanker and @TobiHartmann

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 5f7b007.
Since your change was applied there have been 62 commits pushed to the master branch:

• 4a73ed4: 8330144: Revise os::free_memory()
• 35df48e: 8335860: compiler/vectorization/TestFloat16VectorConvChain.java fails with non-standard AVX/SSE settings
• 7bf5313: 8335480: Only deoptimize threads if needed when closing shared arena
• 1b83bd9: 8336661: Parallel: Remove stacks_empty assert in PSScavenge::invoke
• 72297d2: 8317720: RISC-V: Implement Adler32 intrinsic
• 21a6cf8: 8336587: failure_handler lldb command times out on macosx-aarch64 core file
• 78cc0f9: 8336091: Fix HTML warnings in the generated HTML files
• bcb5e69: 8335921: Fix HotSpot VM build without JVMTI
• 10186ff: 8336300: DateFormatSymbols#getInstanceRef returns non-cached instance
• 7ec55df: 8336638: Parallel: Remove redundant mangle in PSScavenge::invoke
• ... and 52 more: https://git.openjdk.org/jdk/compare/9b6f6c5c9dd6d0fbb056e8d84c3a0888a3320edf...master

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit 5f7b007.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.