RFR: 8254354: Add a withInvokeExactBehavior() VarHandle combinator [v15]
Jorn Vernee
jvernee at openjdk.java.net
Tue Nov 10 18:01:09 UTC 2020
> Hi,
>
> This patch adds an asExact() combinator to VarHandle, that will return a new VarHandle that performs exact type checks, similar to MethodHandle::invokeExact, to help developers catch inexact VarHandle usage, which can lead to performance degradation.
>
> This is implemented using a boolean flag in VarForm. If the flag is set, the exact type of the invocation is checked against the exact type in the VarForm. If there is a mismatch, a WrongMethodTypeException is thrown.
>
> Other than that, there is also an asGeneric() combinator added that does the inverse operation (thanks to Rémi for the suggestion). I've also added The `@Hidden` annotation to the VarHandleGuards methods, as well as a type-checking helper method called from the generic invocation lambda form, so that the stack trace we get points at the location where the VarHandle is being used.
>
> Thanks,
> Jorn
>
> CSR link: https://bugs.openjdk.java.net/browse/JDK-8255375
Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
Add additional asserts to tests checking result of hasInvokeExactBehavior
-------------
Changes:
- all: https://git.openjdk.java.net/jdk/pull/843/files
- new: https://git.openjdk.java.net/jdk/pull/843/files/3097f080..4248f7ee
Webrevs:
- full: https://webrevs.openjdk.java.net/?repo=jdk&pr=843&range=14
- incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=843&range=13-14
Stats: 15 lines in 1 file changed: 14 ins; 0 del; 1 mod
Patch: https://git.openjdk.java.net/jdk/pull/843.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/843/head:pull/843
PR: https://git.openjdk.java.net/jdk/pull/843
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