On Wed, 16 Sep 2026 13:52:17 GMT, Jorn Vernee <[email protected]> wrote:
>> Implement a method handle combinator that can be used to synchronize on an
>> object monitor while executing a given target method handle.
>>
>> The returned method handle behaves similar to the notional code:
>>
>>
>> R adapter(Object lock, A... a) throws Throwable {
>> synchronized (lock) {
>> return body.invokeExact(a...);
>> }
>> }
>>
>>
>> The lambda form is similar to existing ones: we box up all the arguments for
>> the body handle, call a fallback function which synchronizes and invokes the
>> body with the boxed argument, then the `Object` result is fed to an unboxing
>> handle to unbox the result if needed.
>>
>> There's a corresponding intrinsic in `InvokerBytecodeGenerator` which
>> replaces these three operations with `monitorEnter`/`monitorExit`
>> instructions, direct argument/return value forwarding without (un)boxing,
>> and the necessary exception handling which makes sure we unlock the lock
>> again in case the body throws an exception. The generated code is similar to
>> what javac generates.
>>
>> ---------
>> - [x] I confirm that I make this contribution in accordance with the
>> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai).
>
> Jorn Vernee has updated the pull request incrementally with three additional
> commits since the last revision:
>
> - Fix typo
> - Add lambdaform shape comment
> - Add LF interpreter test + var args collector test + use asFixedArity
Otherwise, looks good.
src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 7706:
> 7704:
> 7705: /**
> 7706: * Creates a synchronizing method handle that executes the give
> {@code body}
s/give/given/
-------------
Marked as reviewed by vlivanov (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/32817#pullrequestreview-5239785078
PR Review Comment: https://git.openjdk.org/jdk/pull/32817#discussion_r4040140358
