> 8268829: Provide an optimized way to walk the stack with Class object only > > `StackWalker::walk` creates one `StackFrame` per frame and the current > implementation > allocates one `StackFrameInfo` and one `MemberName` objects per frame. Some > frameworks > like logging may only interest in the Class object but not the method name > nor the BCI, > for example, filters out its implementation classes to find the caller class. > It's > similar to `StackWalker::getCallerClass` but allows a predicate to filter out > the element. > > This PR proposes to add `Option.NO_METHOD_INFO` new stack walking option. > If no method information is needed, this option can be used such that the > stack walker will save the overhead (1) to extract the method information > and (2) the memory used for the stack walking. In addition, this can also > fix > > - [8311500](https://bugs.openjdk.org/browse/JDK-8311500): > StackWalker.getCallerClass() throws UOE if invoked reflectively > > Adding `NO_METHOD_TIME` option provides a simple way for existing code, > for example logging frameworks, to take advantage of this enhancement with > the least change as it can keep the existing implementation in traversing > `StackFrame`s. > > For example: to find the first caller filtering a known list of > implementation class, > existing code can just add `NO_METHOD_INFO` in the call to > `StackWalker::getInstance` > to create a stack walker instance: > > > StackWalker walker = > StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE, NO_METHOD_INFO); > Optional<Class<?>> callerClass = walker.walk(s -> > s.map(StackFrame::getDeclaringClass) > .filter(interestingClasses::contains) > .findFirst()); > > > If method information is accessed on the `StackFrame`s produced by this stack > walker such as > `StackFrame::getMethodName`, then `UnsupportedOperationException` will be > thrown. > > The alternative considered is to provide a new API: > `<T> T walkClass(Function<? super Stream<Class<?>, ? extends T> function)` > > In this case, the caller would need to pass a function that takes a stream > of `Class` object instead of `StackFrame`. Existing code would have to > modify calls to the `walk` method to `walkClass` and the function body. > > ### Implementation Details > > If `NO_METHOD_NAME` is set, the implementation creates `ClassFrameInfo[]` > buffer that is filled by the VM during stack walking. `ClassFrameInfo` > holds the > Class instance plus `flags` which indicate if it's caller sensitive or > hidden. > With this change, `StackWalker::getCa...
Mandy Chung has updated the pull request incrementally with one additional commit since the last revision: clean up ------------- Changes: - all: https://git.openjdk.org/jdk/pull/15370/files - new: https://git.openjdk.org/jdk/pull/15370/files/e9e2b390..87775552 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=15370&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15370&range=00-01 Stats: 6 lines in 4 files changed: 1 ins; 2 del; 3 mod Patch: https://git.openjdk.org/jdk/pull/15370.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/15370/head:pull/15370 PR: https://git.openjdk.org/jdk/pull/15370
