8289558: Need spec clarification of j.l.foreign.*Layout

[mcimadamore]

This patch fixes few javadoc issues in the memory layout API.
The main issues are that SequenceLayout::flatten and SequenceLayout::reshape still mention failures caused by a lack of size. But that condition is no longer possible in the new API.

The javadoc of ValueLayout::arrayElementVarHandle is suboptimal and can be clarified - UOE is only thrown if the value layout alignment is bigger than its size.

Finally, the MemoryLayout::equals method does not mention value layout carriers.

The JBS issue associated with this PR mentions also other issues, mostly related to the overly broad visibility of some of the methods in the javadoc (e.g. isPadding). Unfortunately, given the presence of an intermediate, non-public, abstract class, this is what we get from javadoc. Fixing these issues would require a deeper restructuring of the implementation, which would be too riskt at this stage.

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Issues

• JDK-8289558: Need spec clarification of j.l.foreign.*Layout
• JDK-8289577: Need spec clarification of j.l.foreign.*Layout (CSR)

Reviewers

• Paul Sandoz (@PaulSandoz - Reviewer)
• Jorn Vernee (@JornVernee - Reviewer)

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[mcimadamore]

I've consolidated things a bit here - the superclass should check name, size and alignment - while subclasses should only check additional properties.

[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (c5d3f2b3)
• 00: Full (7d993fe2)

[openjdk]

@mcimadamore 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:

8289558: Need spec clarification of j.l.foreign.*Layout

Reviewed-by: psandoz, jvernee

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At the time when this comment was updated there had been 16 new commits pushed to the master branch:

• 0b6fd48: 8288128: S390X: Fix crashes after JDK-8284161 (Virtual Threads)
• 30e134e: 8289091: move oop safety check from SharedRuntime::get_java_tid() to JavaThread::threadObj()
• 29ea642: 8287847: Fatal Error when suspending virtual thread after it has terminated
• f640fc5: 8067757: Incorrect HTML generation for copied javadoc with multiple @throws tags
• 0dff327: 8289569: [test] java/lang/ProcessBuilder/Basic.java fails on Alpine/musl
• 1a27164: 8287851: C2 crash: assert(t->meet(t0) == t) failed: Not monotonic
• 5b5bc6c: 8287672: jtreg test com/sun/jndi/ldap/LdapPoolTimeoutTest.java fails intermittently in nightly run
• dc4edd3: 8289183: jdk.jfr.consumer.RecordedThread.getId references Thread::getId, should be Thread::threadId
• c4dcce4: 8289619: JVMTI SelfSuspendDisablerTest.java failed with RuntimeException: Test FAILED: Unexpected thread state
• f5cdaba: 8245268: -Xcomp is missing from java launcher documentation
• ... and 6 more: https://git.openjdk.org/jdk19/compare/95497772e7207b5752e6ecace4a6686df2b45227...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[mcimadamore]

/integrate

[openjdk]

Going to push as commit 889150b.
Since your change was applied there have been 24 commits pushed to the master branch:

• 8dd94a2: 8289196: Pattern domination not working properly for record patterns
• 8f24d25: 6509045: {@inheritdoc} only copies one instance of the specified exception
• 9a0fa82: 8288949: serviceability/jvmti/vthread/ContStackDepthTest/ContStackDepthTest.java failing
• 55fa19b: 8289857: ProblemList jdk/jfr/event/runtime/TestActiveSettingEvent.java
• 32b650c: 8289840: ProblemList vmTestbase/nsk/jdwp/ThreadReference/ForceEarlyReturn/forceEarlyReturn002/forceEarlyReturn002.java when run with vthread wrapper
• ef3f2ed: 8289841: ProblemList vmTestbase/gc/gctests/MemoryEaterMT/MemoryEaterMT.java with ZGC on windows
• 0526402: 8289477: Memory corruption with CPU_ALLOC, CPU_FREE on muslc
• b3a0e48: 8289439: Clarify relationship between ThreadStart/ThreadEnd and can_support_virtual_threads capability
• 0b6fd48: 8288128: S390X: Fix crashes after JDK-8284161 (Virtual Threads)
• 30e134e: 8289091: move oop safety check from SharedRuntime::get_java_tid() to JavaThread::threadObj()
• ... and 14 more: https://git.openjdk.org/jdk19/compare/95497772e7207b5752e6ecace4a6686df2b45227...master

Your commit was automatically rebased without conflicts.

[openjdk]

@mcimadamore Pushed as commit 889150b.

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