8361292: Rename ModuleEntry::module() to module_oop() #26102

iklam · 2025-07-02T17:33:40Z

A module has both a Java and a C++ representation

C++: ModuleEntry
Java: java.lang.Module

In C++, we have the following two methods

ModuleEntry* InstanceKlass::module()
oop ModuleEntry::module()

This can lead to confusing code like this:

InstanceKlass* ik = ...;
oop module = ik->module()->module()

Proposal:

Leave InstanceKlass::module() as is -- there's another function with the same style: PackageEntry* InstanceKlass::package()
Rename ModuleEntry::module() to ModuleEntry::module_oop(), so the above example can be more readable:

InstanceKlass* ik = ...;
oop module = ik->module()->module_oop()

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Issue

JDK-8361292: Rename ModuleEntry::module() to module_oop() (Enhancement - P4)

Reviewers

Coleen Phillimore (@coleenp - Reviewer)
Calvin Cheung (@calvinccheung - Reviewer)
Serguei Spitsyn (@sspitsyn - Reviewer)

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bridgekeeper · 2025-07-02T17:34:45Z

👋 Welcome back iklam! 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 · 2025-07-02T17:34:53Z

@iklam 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:

8361292: Rename ModuleEntry::module() to module_oop()

Reviewed-by: coleenp, ccheung, sspitsyn

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 3 new commits pushed to the master branch:

74822ce: 8358183: [JVMCI] crash accessing nmethod::jvmci_name in CodeCache::aggregate
ea86a20: 8357424: [JVMCI] Avoid incrementing decompilation count for hosted compiled nmethod
5e30bf6: 8360116: Add support for AVX10 floating point minmax instruction

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openjdk · 2025-07-02T17:35:32Z

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

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mlbridge · 2025-07-02T17:39:17Z

Webrevs

01: Full - Incremental (f58f2852)
00: Full (69b453e2)

coleenp

I like this change other than precond(). ModuleEntry vs java.lang.Module oops is clearer with a different method name. I've been confused by this too.

coleenp · 2025-07-02T17:50:03Z

src/hotspot/share/runtime/reflection.cpp

-        assert(jlm != nullptr, "Null jlm in module_to ModuleEntry");
-        intptr_t identity_hash = jlm->identity_hash();
+        oop module_oop = module_to->module_oop();
+        precond(module_oop != nullptr);


I don't like precond() when you could have a useful assert message instead.

coleenp · 2025-07-02T17:50:52Z

src/hotspot/share/runtime/reflection.cpp

-        assert(jlm != nullptr, "Null jlm in module_from ModuleEntry");
-        intptr_t identity_hash = jlm->identity_hash();
+        oop module_oop = module_from->module_oop();
+        precond(module_oop != nullptr);


same here. "Module oop should be non-null in ModuleEntry"

We have just read the oop from the module entry and assert that it's not null, so the original message didn't add any extra information. That's why I removed it.

I have added back a message, "should have been initialized".

The real story is more complex, but I think this message willl give enough hints -- the module oop is usually initialized inside the ModuleEntry constructor, except for a few cases for the java.base module where the module oop is retroactively updated. In any case, by the time we reach this assert, the module oop must have been initialized in one of those possible paths.

calvinccheung

Looks good.

calvinccheung · 2025-07-02T21:25:04Z

src/hotspot/share/classfile/moduleEntry.cpp

 ModuleEntry* ModuleEntryTable::_javabase_module = nullptr;

-oop ModuleEntry::module() const { return _module.resolve(); }
+oop ModuleEntry::module_oop() const { return _module_handle.resolve(); }


(Pre-existing) Just wondering why this one-liner function doesn't reside in the moduleEntry.hpp?

I think it's because OopHandle::resolve() is an inline function, but we are not allowed to include xxx.inline.hpp in non-inlined .hpp files.

sspitsyn

Looks good.

iklam · 2025-07-03T16:50:52Z

Thanks @coleenp @calvinccheung @sspitsyn for the review
/integrate

openjdk · 2025-07-03T16:52:22Z

Going to push as commit 66836d4.
Since your change was applied there have been 13 commits pushed to the master branch:

3daa03c: 8358680: AOT cache creation fails: no strings should have been added
24117c6: 8349188: LineBorder does not scale correctly
5e40fb6: 8277394: Remove the use of safepoint_workers in reference processor
... and 10 more: https://git.openjdk.org/jdk/compare/c50370599e40bfaeccba9aa6b28da661129f9450...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-07-03T16:52:34Z

@iklam Pushed as commit 66836d4.

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

8361292: Rename ModuleEntry::module() to module_oop()

69b453e

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f58f285

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8361292: Rename ModuleEntry::module() to module_oop() #26102

8361292: Rename ModuleEntry::module() to module_oop() #26102

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