8298727: Trees.getPath may crash for unnamed package

[lahodaj]

Considering an empty package-info.java file is normally accepted by javac (as a package-info for the unnamed module). But, if Trees.getPath is used on the unnamed package, a NPE occurs:

java.lang.NullPointerException: Cannot invoke "com.sun.tools.javac.tree.JCTree.accept(com.sun.tools.javac.tree.JCTree$Visitor)" because "tree" is null
at jdk.compiler/com.sun.tools.javac.tree.TreeInfo.declarationFor(TreeInfo.java:811)
at jdk.compiler/com.sun.tools.javac.model.JavacElements.getTreeAndTopLevel(JavacElements.java:779)
at jdk.compiler/com.sun.tools.javac.model.JavacElements.getTreeAndTopLevel(JavacElements.java:799)
at jdk.compiler/com.sun.tools.javac.api.JavacTrees.getPath(JavacTrees.java:331)
at jdk.compiler/com.sun.tools.javac.api.JavacTrees.getPath(JavacTrees.java:321)

The reason is that Env.tree is initialized to the package clause in Enter.visitTopLevel, but when the package clause is missing, Env.tree is null, leading to the error above.

The proposed fix is to set Env.tree to the top-level tree in this case, to keep it non-null. As the empty package-info can be compiled, it seems reasonable for the model to work on is as well, so a non-null tree needs to be set, and there's no other tree that could be used, I believe.

---

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-8298727: Trees.getPath may crash for unnamed package

Reviewers

• Vicente Romero (@vicente-romero-oracle - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk20 pull/31/head:pull/31
$ git checkout pull/31

Update a local copy of the PR:
$ git checkout pull/31
$ git pull https://git.openjdk.org/jdk20 pull/31/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 31

View PR using the GUI difftool:
$ git pr show -t 31

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk20/pull/31.diff

[bridgekeeper]

👋 Welcome back jlahoda! 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]

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

• compiler

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 (7138b1a0)

[vicente-romero-oracle]

looks sensible

[openjdk]

@lahodaj 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:

8298727: Trees.getPath may crash for unnamed package

Reviewed-by: vromero

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 6 new commits pushed to the master branch:

• 581f9f2: 8297235: ZGC: assert(regs[i] != regs[j]) failed: Multiple uses of register: rax
• 0eeaf6b: 8298649: JFR: RemoteRecordingStream support for checkpoint event sizes beyond u4
• 2791701: 8298296: gc/TestFullGCCount.java fails with "System.gc collections miscounted."
• 0bbc418: 8294902: Undefined Behavior in C2 regalloc with null references
• 9bcdfc4: 8298425: System.console().readLine() hangs in jshell
• 27d4971: 8298520: C2: assert(found_opaque == res) failed: wrong pattern

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.

[lahodaj]

Thanks for the review, Vicente!

[lahodaj]

/integrate

[openjdk]

Going to push as commit 22a6b59.
Since your change was applied there have been 9 commits pushed to the master branch:

• 323e574: 8298371: monitors_on_stack extracts unprocessed oops
• 80cadd4: 8298785: gc/TestFullGCCount.java fails with "invalid boolean value: null' for expression vm.opt.ExplicitGCInvokesConcurrent'"
• ebc4710: 8298277: Replace "session" with "scope" for FFM access
• 581f9f2: 8297235: ZGC: assert(regs[i] != regs[j]) failed: Multiple uses of register: rax
• 0eeaf6b: 8298649: JFR: RemoteRecordingStream support for checkpoint event sizes beyond u4
• 2791701: 8298296: gc/TestFullGCCount.java fails with "System.gc collections miscounted."
• 0bbc418: 8294902: Undefined Behavior in C2 regalloc with null references
• 9bcdfc4: 8298425: System.console().readLine() hangs in jshell
• 27d4971: 8298520: C2: assert(found_opaque == res) failed: wrong pattern

Your commit was automatically rebased without conflicts.

[openjdk]

@lahodaj Pushed as commit 22a6b59.

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