On Thu, 29 Oct 2020 18:14:05 GMT, Jorn Vernee <jver...@openjdk.org> wrote:
>> 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 with a new target base due to a > merge or a rebase. The incremental webrev excludes the unrelated changes > brought in by the merge/rebase. The pull request contains 12 additional > commits since the last revision: > > - Update Javadoc, and rename asExact and asGeneric to > withInvokeExactBehaviour and withInvokeBehaviour > - Merge branch 'master' into Exact_VarHandle > - Use AccessType ordinal in guard checks instead of the AccessMode ordinal > - Update accessModeType to use the AccessType ordinal directly. > - Add benchmarks > - - Update javadoc > - Make isExact() public > - Fixes failing tests, and enable verifier on Exact test > - Fix whitespace > - Comment out VarHandleGuards generator code > - Makes exactness a property of a VarHandle, not a VarForm, since the latter > are shared. Use handle.accessModeType to get the exact type of the VarHandle. > - ... and 2 more: > https://git.openjdk.java.net/jdk/compare/08226775...3c707bc7 Looks good. There is just one difference between the spec and implementation. The spec states: > If this VarHandle already has invoke{-exact} behaviour this VarHandle is > returned. I prefer this behaviour, but feel free to update the spec if you like e.g. If ... already has XXX then a new VH with exactly the same behaviour as this VH is returned. I just realized i used "behaviour", the english spelling. We should use the US spelling, "behavior", which is more commonly used throughout the JDK documentation. ------------- Marked as reviewed by psandoz (Reviewer). PR: https://git.openjdk.java.net/jdk/pull/843
