8366498: Simplify ClassFileParser::parse_super_class #27026

iklam · 2025-09-01T05:19:43Z

The if cp->resolved_klass_at() is never true called because we are very early in class file parsing, so no klass CP entries have been resolved at this point.

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Issue

JDK-8366498: Simplify ClassFileParser::parse_super_class (Enhancement - P4)

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David Holmes (@dholmes-ora - Reviewer)
Coleen Phillimore (@coleenp - Reviewer) Review applies to 256716fc

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…class

bridgekeeper · 2025-09-01T05:20:23Z

👋 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 · 2025-09-01T05:20:49Z

@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:

8366498: Simplify ClassFileParser::parse_super_class

Reviewed-by: dholmes, coleenp

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At the time when this comment was updated there had been 7 new commits pushed to the master branch:

986ecff: 8366849: Problemlist jdk/jshell/ToolSimpleTest.java as generic-all
1495dd9: 8366778: Sort share/asm, share/gc, share/include includes
222ae36: 8366688: G1: Rename G1HeapRegionRemSet::is_added_to_cset_group() to has_cset_group()
... and 4 more: https://git.openjdk.org/jdk/compare/90a2db1ecbc3ea25a8e9f15b34a3d8f3941b60d0...master

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openjdk · 2025-09-01T05:21:19Z

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

hotspot-runtime

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 · 2025-09-01T05:25:17Z

Webrevs

dholmes-ora

This does correct the cast but as you suggest this code should actually be unreachable - is_klass() will fail as no classes have been resolved at this stage of classfile parsing,

iklam · 2025-09-01T07:13:52Z

This does correct the cast but as you suggest this code should actually be unreachable - is_klass() will fail as no classes have been resolved at this stage of classfile parsing,

I removed the code for checking is_klass(). I added an assert() and it doesn't get hit at all in local testing. For curiosity, I will run it through the JCK and to see if we ever come here with a resolved class. I will remove the assert in the final version.

src/hotspot/share/classfile/classFileParser.cpp

dholmes-ora

Amazing how one incorrect cast led to that cascade of code changes. :)

Overall seems valid. A couple of nits.

Thanks

dholmes-ora · 2025-09-01T07:39:14Z

src/hotspot/share/classfile/classFileParser.cpp

+  } else {
+    assert(_class_name == vmSymbols::java_lang_Object(), "already checked");
+    _super_klass = nullptr;


This seems unnecessary. We have already check the name and _super_klass is initialized to null.

I think it help people who wonder why _super_klass is not updated in this case. Maybe I can change the assignment to

asssert(_super_klass == nullptr, "already initialized");

I would just have:

else { // The class is Object - so no superclass }

My asserts say the same thing, except they comes with proofs that they are not lying.

I don't like the 'else' either.

I've removed the trailing else and shuffled the asserts around as @coleenp suggested.

coleenp

It's a minor point really but while you're making this logic less confusing, might as well fix the extra else.

coleenp · 2025-09-03T11:24:25Z

src/hotspot/share/classfile/classFileParser.cpp

@@ -5777,8 +5768,8 @@ void ClassFileParser::post_process_parsed_stream(const ClassFileStream* const st
                       "java.lang.Object cannot implement an interface in class file %s",
                       CHECK);
  }


This is somewhat strange logic. Seems like there should be an assert that _super_klass == nullptr then an 'else' at 5779 and an assert that _super_class_index != 0. The trailing else is confusing and it checks something here at 5775.

coleenp · 2025-09-03T11:24:58Z

src/hotspot/share/classfile/classFileParser.cpp

+  } else {
+    assert(_class_name == vmSymbols::java_lang_Object(), "already checked");
+    _super_klass = nullptr;


I don't like the 'else' either.

coleenp

This makes a lot more sense.

…-super-class

dholmes-ora

Looks good. Thanks

iklam · 2025-09-04T16:18:27Z

Thanks @dholmes-ora @coleenp for the review
/integrate

openjdk · 2025-09-04T16:19:35Z

Going to push as commit 79a1a98.
Since your change was applied there have been 12 commits pushed to the master branch:

e190355: 8365467: Issues with jrtfs implementation for exploded run-time images
80873a0: 8366836: Don't execute post-IncludeCustomExtension if file was not included
8c50bed: 8366872: Wrong number of template arguments in test in test_rbtree.cpp
... and 9 more: https://git.openjdk.org/jdk/compare/90a2db1ecbc3ea25a8e9f15b34a3d8f3941b60d0...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-09-04T16:19:42Z

@iklam Pushed as commit 79a1a98.

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

8366498: Wrong InstanceKlass::cast() in ClassFileParser::parse_super_…

d353bfe

…class

openjdk bot added hotspot-runtime hotspot-runtime-dev@openjdk.org rfr Pull request is ready for review labels Sep 1, 2025

dholmes-ora reviewed Sep 1, 2025

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Simplify parse_super_klass() -> check_super_class()

dec4af7

iklam changed the title ~~8366498: Wrong InstanceKlass::cast() in ClassFileParser::parse_super_class~~ 8366498: Simplify ClassFileParser::parse_super_class Sep 1, 2025

dholmes-ora reviewed Sep 1, 2025

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src/hotspot/share/classfile/classFileParser.cpp Outdated Show resolved Hide resolved

dholmes-ora reviewed Sep 1, 2025

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removed test-only assert

256716f

dholmes-ora approved these changes Sep 1, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Sep 1, 2025

coleenp suggested changes Sep 3, 2025

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coleenp approved these changes Sep 3, 2025

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iklam added 2 commits September 3, 2025 22:39

@coleenp review - updated asserts

8390278

Merge branch 'master' into 8366498-wrong-instance-klass-cast-in-parse…

4422804

…-super-class

openjdk bot removed the ready Pull request is ready to be integrated label Sep 4, 2025

dholmes-ora approved these changes Sep 4, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Sep 4, 2025

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openjdk bot closed this Sep 4, 2025

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Sep 4, 2025

8366498: Simplify ClassFileParser::parse_super_class #27026

8366498: Simplify ClassFileParser::parse_super_class #27026

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