Skip VarHandle init when unaligned access is supported#16664
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normanmaurer merged 3 commits intoApr 21, 2026
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PR for 5.0 #16676 |
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`initializeVarHandle()`. This made VarHandle code reachable even when Unsafe is available, causing Truffle/Polyglot native-image builds to fail with `MethodHandle.linkToStatic` blocklist violations (#16607). Restoring the original Unsafe guard fixes #16607, but also kills Use `isUnaligned()` as the guard instead. On platforms where unaligned access is known (x86, modern ARM), Unsafe already handles multi-byte access fine, so VarHandle isn't needed and VarHandleFactory stays unreachable. On platforms where UNALIGNED is unknown (exactly the case #16207 targets), VarHandle still gets initialized and works as before. Fixes #16607. Tested with the reporter's project (https://github.com/adamdickmeiss/vertx-graalvm-native-image-log4j): - Before: `=== Found 4 compilation blocklist violations ===` BUILD FAILURE - After: No violations, BUILD SUCCESS Co-authored-by: Chris Vest <christianvest_hansen@apple.com> Co-authored-by: DoeonSong <96420547+Songdoeon@users.noreply.github.com> Co-authored-by: Chris Vest <christianvest_hansen@apple.com>
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Motivation
#16207 removed the
UNSAFE_UNAVAILABILITY_CAUSE == nullguard frominitializeVarHandle(). This made VarHandle code reachable even when Unsafe is available,causing Truffle/Polyglot native-image builds to fail with
MethodHandle.linkToStaticblocklist violations (#16607).Restoring the original Unsafe guard fixes #16607, but also kills #16207's core feature (VarHandle fallback when UNALIGNED is unknown).
Modification
Use
isUnaligned()as the guard instead. On platforms where unaligned access is known (x86, modern ARM), Unsafe already handles multi-byte access fine, so VarHandleisn't needed and VarHandleFactory stays unreachable.
On platforms where UNALIGNED is unknown (exactly the case #16207 targets), VarHandle still gets initialized and works as before.
Result
Fixes #16607.
Tested with the reporter's project (https://github.com/adamdickmeiss/vertx-graalvm-native-image-log4j):
=== Found 4 compilation blocklist violations ===BUILD FAILURE