8337785: Fix simple -Wzero-as-null-pointer-constant warnings in x86 code

[kimbarrett]

Please review this trivial change that replaces some uses of literal 0 as a
null pointer constant in x86 code to instead use nullptr.

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-8337785: Fix simple -Wzero-as-null-pointer-constant warnings in x86 code (Enhancement - P4)

Reviewers

• Julian Waters (@TheShermanTanker - Committer)
• Albert Mingkun Yang (@albertnetymk - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/20453/head:pull/20453
$ git checkout pull/20453

Update a local copy of the PR:
$ git checkout pull/20453
$ git pull https://git.openjdk.org/jdk.git pull/20453/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 20453

View PR using the GUI difftool:
$ git pr show -t 20453

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/20453.diff

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[bridgekeeper]

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[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:

8337785: Fix simple -Wzero-as-null-pointer-constant warnings in x86 code

Reviewed-by: jwaters, ayang, shade

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 8 new commits pushed to the master branch:

• c095c0e: 8336489: Track scoped accesses in JVMCI compiled code
• 7e925d7: 8337283: configure.log is truncated when build dir is on different filesystem
• 2e093b0: 8337779: test/jdk/jdk/jfr/jvm/TestHiddenWait.java is a bit fragile
• d3e7b0c: 8336462: ConcurrentSkipListSet Javadoc incorrectly warns about size method complexity
• be34730: 8335257: Refactor code to create Initialized Assertion Predicates into separate class
• fbe8a81: 8333144: docker tests do not work when ubsan is configured
• dabdae6: 8334599: Improve code from JDK-8302671
• 8bd3cd5: 8337716: ByteBuffer hashCode implementations are inconsistent

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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]

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[mlbridge]

Webrevs

• 00: Full (48b37184)

[TheShermanTanker]

There really are a lot of these, aren't there? :P

[kimbarrett]

There really are a lot of these, aren't there? :P

Yeah, there were many thousand when I started, though a lot were from a small number of places in widely included
headers. The large number of PRs is because I've been breaking things up into mostly trivial (or at least simple) changes
in focused areas, to make any given review easy.

In the home stretch. There are a couple more like the current batch, and then some small but more complex ones,
including one or two where I think there might be an actual bug involved.

I'm only planning to enable the warning with gcc for now. Enabling for clang would require testing on platforms I don't
have (easy, or any) access to. I also won't be testing your windows/gcc work, so enabling the warning will likely break
that, even if all the shared and cpu-specific cases are dealt with.

[TheShermanTanker]

There really are a lot of these, aren't there? :P

Yeah, there were many thousand when I started, though a lot were from a small number of places in widely included headers. The large number of PRs is because I've been breaking things up into mostly trivial (or at least simple) changes in focused areas, to make any given review easy.

In the home stretch. There are a couple more like the current batch, and then some small but more complex ones, including one or two where I think there might be an actual bug involved.

I'm only planning to enable the warning with gcc for now. Enabling for clang would require testing on platforms I don't have (easy, or any) access to. I also won't be testing your windows/gcc work, so enabling the warning will likely break that, even if all the shared and cpu-specific cases are dealt with.

Good to have a rundown on the problem, thanks. I can deal with the breakages in the Windows/gcc Port, no worries :)

[shipilev]

Looks fine.

[kimbarrett]

Thanks for reviews @TheShermanTanker , @albertnetymk , and @shipilev

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 431d4f7.
Since your change was applied there have been 16 commits pushed to the master branch:

• e2c07d5: 8337299: vmTestbase/nsk/jdb/stop_at/stop_at002/stop_at002.java failure goes undetected
• 08f697f: 8337819: Update GHA JDKs to 22.0.2
• 42652b2: 8337787: Fix -Wzero-as-null-pointer-constant warnings when JVMTI feature is disabled
• 807186f: 8337784: Fix simple -Wzero-as-null-pointer-constant warnings in linux/posix code
• e68df52: 8337054: JDK 23 RDP2 L10n resource files update
• 9856216: 8336928: GHA: Bundle artifacts removal broken
• 219e1eb: 8337712: Wrong javadoc in java.util.Date#toString(): "61" and right parenthesis
• 97afbd9: 8336410: runtime/NMT/TotalMallocMmapDiffTest.java Total malloc diff is incorrect. Expected malloc diff range
• c095c0e: 8336489: Track scoped accesses in JVMCI compiled code
• 7e925d7: 8337283: configure.log is truncated when build dir is on different filesystem
• ... and 6 more: https://git.openjdk.org/jdk/compare/367e0a65561f95aad61b40930d5f46843fee3444...master

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit 431d4f7.

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