On Wed, 27 Oct 2021 20:16:54 GMT, Mandy Chung <mch...@openjdk.org> wrote:
>> This reimplements core reflection with method handles. >> >> For `Constructor::newInstance` and `Method::invoke`, the new implementation >> uses `MethodHandle`. For `Field` accessor, the new implementation uses >> `VarHandle`. For the first few invocations of one of these reflective >> methods on a specific reflective object we invoke the corresponding method >> handle directly. After that we spin a dynamic bytecode stub defined in a >> hidden class which loads the target `MethodHandle` or `VarHandle` from its >> class data as a dynamically computed constant. Loading the method handle >> from a constant allows JIT to inline the method-handle invocation in order >> to achieve good performance. >> >> The VM's native reflection methods are needed during early startup, before >> the method-handle mechanism is initialized. That happens soon after >> System::initPhase1 and before System::initPhase2, after which we switch to >> using method handles exclusively. >> >> The core reflection and method handle implementation are updated to handle >> chained caller-sensitive method calls [1] properly. A caller-sensitive >> method can define with a caller-sensitive adapter method that will take an >> additional caller class parameter and the adapter method will be annotated >> with `@CallerSensitiveAdapter` for better auditing. See the detailed >> description from [2]. >> >> Ran tier1-tier8 tests. >> >> [1] https://bugs.openjdk.java.net/browse/JDK-8013527 >> [2] >> https://bugs.openjdk.java.net/browse/JDK-8271820?focusedCommentId=14439430&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14439430 > > Mandy Chung has updated the pull request with a new target base due to a > merge or a rebase. The pull request now contains 43 commits: > > - fix copyright header and typo > - improve documentation of AccessorUtils > - Merge branch 'master' of https://github.com/openjdk/jdk into > reimplement-method-invoke > - Fall back to the VM native reflection support if method handle cannot be > created > - fix bug id in test > - Merge > - Merge branch 'master' of https://github.com/openjdk/jdk into > reimplement-method-invoke > - Merge branch 'master' of https://github.com/openjdk/jdk into > reimplement-method-invoke > - Separate paramFlgas into paramCount and flags fields > - Minor cleanup. Improve javadoc in CallerSensitiveAdapter > - ... and 33 more: > https://git.openjdk.java.net/jdk/compare/9a3e9542...46cb306b I further looked at the specification and implementation of `Field::set` and adding `java.lang.reflect` to the trusted final field package list does not relate to this issue. I was confused with the `isTrustedFinalField` check which is supposed to check if the given `Field` object has read-only access. A `Field` object has write access if and only if - setAccessible(true) has succeeded for this Field object; - the field is non-static; and - the field's declaring class is not a hidden class; and - the field's declaring class is not a record class. The hack dropping `final` from a static final `Field` make a `Field` object which has only read-only access to get write access. With JEP 416, this hack no longer works because the read-only access is set according to the original field modifiers but not the `Field` object. ------------- PR: https://git.openjdk.java.net/jdk/pull/5027
