8324686: Remove redefinition of NULL for MSVC

[kimbarrett]

Please review this change that removes the redefinition of NULL in
globalDefinitions_visCPP.hpp. That redefinition was to support the use of NULL
in a varargs context, because of the size difference for int vs a pointer.
However, we no longer have any direct uses of NULL in HotSpot, and have a test
that ensures there is no backsliding.

There may be indirect uses of NULL via third-party libraries. Such uses could
have been in the scope of the removed redefinition. But those uses must have
been correct even without the redefinition, else they would be incorrect for
non-HotSpot users.

Testing: mach5 tier1-3, GHA sanity tests

---

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-8324686: Remove redefinition of NULL for MSVC (Enhancement - P4)

Reviewers

• Aleksey Shipilev (@shipilev - Reviewer)
• David Holmes (@dholmes-ora - Reviewer)

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/24537/head

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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:

8324686: Remove redefinition of NULL for MSVC

Reviewed-by: shade, dholmes

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At the time when this comment was updated there had been 30 new commits pushed to the master branch:

• 45b7c74: 8341641: Make %APPDATA% and %LOCALAPPDATA% env variables available in *.cfg files
• 5c438c5: 8352748: Remove com.sun.tools.classfile from the JDK
• e87ff32: 8351034: Add AVX-512 intrinsics for ML-DSA
• ... and 27 more: https://git.openjdk.org/jdk/compare/473251dbb308016ccda6c88fd36bd10c81e65865...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.

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[openjdk]

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[mlbridge]

Webrevs

• 00: Full (cdce8438)

[shipilev]

Looks fine. So, just to be extra clear, this would only affect Hotspot, not JDK. There are no interesting hits for NULL-s right now in Hotspot code. There are still lots of NULL-s in JDK native code.

[kimbarrett]

Looks fine. So, just to be extra clear, this would only affect Hotspot, not JDK. There are no interesting hits for NULL-s right now in Hotspot code. There are still lots of NULL-s in JDK native code.

That's correct. And there's a test to keep it that way:
https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/sources/TestNoNULL.java

[dholmes-ora]

Looks fine. Thanks for cleaning this up.

[kimbarrett]

Thanks for reviews @shipilev and @dholmes-ora .

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 6c26670.
Since your change was applied there have been 39 commits pushed to the master branch:

• 51b3d6b: 8352431: java/net/httpclient/EmptyAuthenticate.java uses "localhost"
• 9a3f999: 8346236: Auto vectorization support for various Float16 operations
• 6545e0d: 8353189: [ASAN] memory leak after 8352184
• ... and 36 more: https://git.openjdk.org/jdk/compare/473251dbb308016ccda6c88fd36bd10c81e65865...master

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit 6c26670.

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