RFR: 8242451: ensure semantics of non-capturing lambdas are preserved independent of execution mode
Mandy Chung
mchung at openjdk.java.net
Wed Sep 9 16:43:45 UTC 2020
On Wed, 9 Sep 2020 12:19:04 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:
>> [JDK-8232806](https://bugs.openjdk.java.net/browse/JDK-8232806) introduced the
>> jdk.internal.lambda.disableEagerInitialization system property to be able to disable eager initialization of lambda
>> classes. This was necessary to prevent side effects of class initializers triggered by such initialization in the
>> context of the GraalVM native image tool. However, the change as it is implemented means that the behaviour of
>> non-capturing lambdas depends on the value of `disableEagerInitialization`: when it is false (the default) such lambdas
>> are actually a singleton while when it is true, a fresh instance is returned every time. Programs should definitely
>> _not_ rely on reference equality since the Java spec does not guarantee it. However, in order to separate concern and
>> ease debugging such bad programs, `disableEagerInitialization` shouldn't influence the singleton vs. fresh instance
>> behaviour of lambdas in either direction.
>
> test/langtools/tools/javac/lambda/lambdaExpression/LambdaTest6.java line 29:
>
>> 27: * @summary Add lambda tests
>> 28: * Test bridge methods for certain SAM conversions
>> 29: * Test the set of generate fields
>
> I would suggest to consider having the test under test/jdk/(java/lang/invoke/lambda), not under
> test/langtools/tools/javac.
It's a good suggestion as `disableEagerInitialization` support is not part of javac.
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PR: https://git.openjdk.java.net/jdk/pull/93
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