8301612: OopLoadProxy constructor should be explicit

[xmas92]

The implicit conversion via constructor OopLoadProxy(P* addr) can cause problems when using the access API and nullptr.
For example code like

oop o = (_obj == NULL) ? nullptr : NativeAccess<>::oop_load(_obj);

will compile but is wrong and will crash.
This is because it will be interpreted as:

oop o = static_cast<oop>((_obj == NULL) ? OopLoadProxy(nullptr) : NativeAccess<>::oop_load(_obj));

while the intent of the programmer probably was:

oop o = (_obj == NULL) ? (oop)nullptr : NativeAccess<>::oop_load(_obj);

or more explicitly:

oop o = (_obj == NULL) ? static_cast<oop>(nullptr) : static_cast<oop>(NativeAccess<>::oop_load(_obj));

Marking OopLoadProxy(P* addr) explicit will make this example, and similar code not compile.

---

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-8301612: OopLoadProxy constructor should be explicit

Reviewers

• Stefan Karlsson (@stefank - Reviewer)
• Johan Sjölen (@jdksjolen - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/12364/head:pull/12364
$ git checkout pull/12364

Update a local copy of the PR:
$ git checkout pull/12364
$ git pull https://git.openjdk.org/jdk pull/12364/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 12364

View PR using the GUI difftool:
$ git pr show -t 12364

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/12364.diff

[bridgekeeper]

👋 Welcome back aboldtch! 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]

@xmas92 The following label will be automatically applied to this pull request:

• hotspot

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

[mlbridge]

Webrevs

• 00: Full (0a01d63b)

[stefank]

Looks good and can be considered "trivial".

[openjdk]

@xmas92 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:

8301612: OopLoadProxy constructor should be explicit

Reviewed-by: stefank, jsjolen

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 4 new commits pushed to the master branch:

• bc750f7: 8294527: Some java.security.debug options missing from security docs
• 7c6a8db: 8301447: [REDO] CodeHeap has virtual methods that are not overridden
• cae577a: 8295486: Inconsistent constant field values observed during compilation
• 969f6a3: 8301093: C2 fails assert(ctrl == kit.control()) failed: Control flow was added although the intrinsic bailed out

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.

[jdksjolen]

Thanks for this.

[xmas92]

/integrate

[openjdk]

Going to push as commit 21c1afb.
Since your change was applied there have been 30 commits pushed to the master branch:

• 03b23a1: 8301367: Add exception handler method to the BaseLdapServer
• 7b6ac41: 8286876: NMT.test_unaliged_block_address_vm_assert fails if using clang toolchain
• d097b5e: 8301508: Replace NULL with nullptr in os_cpu/linux_s390
• c8307e3: 8301500: Replace NULL with nullptr in os_cpu/aix_ppc
• 218223e: 8301501: Replace NULL with nullptr in os_cpu/bsd_aarch64
• b81f0ff: 8301505: Replace NULL with nullptr in os_cpu/linux_arm
• 42a286a: 8301511: Replace NULL with nullptr in os_cpu/linux_zero
• ad79e49: 8301512: Replace NULL with nullptr in os_cpu/windows_aarch64
• 8cc399b: 8301503: Replace NULL with nullptr in os_cpu/bsd_zero
• c109dae: 8301513: Replace NULL with nullptr in os_cpu/windows_x86
• ... and 20 more: https://git.openjdk.org/jdk/compare/2a8ae2ff1c95cb75f315eb5340bff2b46409d1ae...master

Your commit was automatically rebased without conflicts.

[openjdk]

@xmas92 Pushed as commit 21c1afb.

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