On Tue, 19 Nov 2024 16:35:44 GMT, Chen Liang <li...@openjdk.org> wrote:
>> src/java.base/share/classes/jdk/internal/reflect/MethodHandleAccessorFactory.java >> line 430: >> >>> 428: // Single parameter of declared type Object[] >>> 429: Class<?>[] parameters = >>> reflectionFactory.getExecutableSharedParameterTypes(method); >>> 430: return parameters.length == 1 && parameters[0] == >>> Object[].class; >> >> Would it be possible to check for the `PolymorphicSignature` annotation >> instead? > > I think the main problem with annotation is that annotation creation needs to > use `java.lang.reflect.Proxy`, which is unavailable until module system is > initialized. Extra allocations are costs too, while checks here only reuse > existing objects. > > In fact, I don't think Java's core libraries ever check for annotations, and > the annotation's support class, `jdk.internal.reflect.ConstantPool`, has > always been only loaded but never initialized in a simple hello world program > since Java 5. In fact, another solution I have contemplated is to update `JavaLangInvokeAccess` implementations. 4 methods in it, `unreflectConstructor`, `unreflectField`, `findVirtual`, and `findStatic`, are exclusively used by core reflection. That solution proposes to bypass `findVirtualForMH`/`findVirtualForVH` and bypass `setVarargs(MemberName)` in `getDirectMethodCommon`/`getDirectConstructorCommon` in these internal hooks. But I think this may be too invasive and unfriendly to backports (also note: backport to 21 isn't clean, there is a small conflict in doc comments), and using native instead of MH for these 2 corner cases shouldn't be too big of a performance concern. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/22169#discussion_r1848704448
