8321467: MemorySegment.setString(long, String, Charset) throws IAE(Misaligned access)

[mcimadamore]

This PR fixes a couple of aligned accesses when reading/writing strings. Such aligned accesses crept in when we optimized string read/write operations to work in bulk. As a result, depending on the maximum alignment constraints supported by the heap segment, some string operations might fail.

I've added some tests to make sure that all operations work as expected with unaligned semantics.

Note: I've considered inferring an alignment constraint from the provided charset, and then use aligned operations (and document that behavior), but I found that to be unsatisfactory: memory operations typically accept a layout, which allow clients to opt out from alignment checks if needed. But if we always infer an alignment constraint from the provided charset, clients would find themselves w/o an escape hatch. For this reason, I think the best way to fix this is to use unaligned operations when reading/writing the string.

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Issue

• JDK-8321467: MemorySegment.setString(long, String, Charset) throws IAE(Misaligned access) (Bug - P3)

Reviewers

• Per Minborg (@minborg - Reviewer)

Reviewing

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[openjdk]

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[mlbridge]

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• 01: Full - Incremental (12cf9e3a)
• 00: Full (856d3e14)

[minborg]

LGTM. Testing looks solid.

[openjdk]

@mcimadamore This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8321467: MemorySegment.setString(long, String, Charset) throws IAE(Misaligned access)

Reviewed-by: pminborg

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At the time when this comment was updated there had been 18 new commits pushed to the master branch:

• 632a3c5: 8305825: getBounds API returns wrong value resulting in multiple Regression Test Failures on Ubuntu 23.04
• 75a7c19: 8315827: Kitchensink.java and RenaissanceStressTest.java time out with jvmti module errors
• 91ffdfb: 8320365: IPPPrintService.getAttributes() causes blanket re-initialisation
• 50baaf4: 8321013: Parallel: Refactor ObjectStartArray
• afb8964: 8320443: [macos] Test java/awt/print/PrinterJob/PrinterDevice.java fails on macOS
• 82796bd: 8320570: NegativeArraySizeException decoding >1G UTF8 bytes with non-ascii characters
• 781775d: 8321484: Make TestImplicitlyDeclaredClasses release independent
• b02fc86: 8321122: Shenandoah: Remove ShenandoahLoopOptsAfterExpansion flag
• 2830dd2: 8321410: Shenandoah: Remove ShenandoahSuspendibleWorkers flag
• f482260: 8319969: os::large_page_init() turns off THPs for ZGC
• ... and 8 more: https://git.openjdk.org/jdk/compare/7fbfb3b74a283261027e6c293e1a5dbc354cf0af...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.

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[mcimadamore]

/integrate

[openjdk]

Going to push as commit 42bb852.
Since your change was applied there have been 28 commits pushed to the master branch:

• c087e91: 8321505: JFR: Update views
• ead4fb1: 8321519: Typo in exception message
• b5933b1: 8320805: JFR: Create view for deprecated methods
• 29d7a22: 8321270: Virtual Thread.yield consumes parking permit
• 0b0fa47: 8319925: CSS.BackgroundImage incorrectly uses double-checked locking
• 0048f1d: 8263256: Test java/net/Inet6Address/serialize/Inet6AddressSerializationTest.java fails due to dynamic reconfigurations of network interface during test
• 49fff01: 8211238: @deprecated JFR event
• 656b446: 8320969: Shenandoah: Enforce stable number of GC workers
• 9a87e52: 8320538: Obsolete CSS styles in collection framework doc-file
• 03c4595: 8321164: javac with annotation processor throws AssertionError: Filling jrt:/... during JarFileObject[/...]
• ... and 18 more: https://git.openjdk.org/jdk/compare/7fbfb3b74a283261027e6c293e1a5dbc354cf0af...master

Your commit was automatically rebased without conflicts.

[openjdk]

@mcimadamore Pushed as commit 42bb852.

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