On Sat, 28 Mar 2026 02:24:14 GMT, Yasumasa Suenaga <[email protected]> wrote:
> On the review for [JDK-8380955](https://bugs.openjdk.org/browse/JDK-8380955) > (#30443), `Linker` and `FunctionDescriptor` do not need to be value based > class because they would not be treated as "value". > `Linker` is defined as providing a way to look up the canonical layouts > associated with the data types used by the ABI. `FunctionDescriptor` > represents the signature of a foreign function. They are not "value". > > Actually they and their child (final) classes do not have `@ValueBased`, thus > `javac` and `-XX:DiagnoseSyncOnValueBasedClasses` cannot identify if they are > used in anti-pattern of value based class. Thus this change does not change > behavior, just documentation updates. > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai). > @mcimadamore I left the reply for [#30443 > (comment)](https://github.com/openjdk/jdk/pull/30443#issuecomment-4161141979) > here. > > > For instance, the Linker uses FD as keys in maps > > Can you show some example(s)? I checked JDK source with `grep -nr > FunctionDescriptor * | grep Map`, but I couldn't find out. (I know that might > not be enough) https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/jdk/internal/foreign/abi/AbstractLinker.java#L88 > > In `FunctionDescriptor`, it might be used like in above, but I feel it is > tricky because the caller have to know return type and argument types when > calling. I think `MethodHandle` is equivalent with function pointer, and > `FunctionDescriptor` is equivalent with `typedef` for the function in C. In > that context, I feel it is no (or rare) use case to treat > `FunctionDescriptor` as "value". I'm not seeing what the problem is here. If you have a function descriptor for `(JAVA_INT)->JAVA_LONG` it might be sometimes helpful to compare it (maybe, eventually, with `==`) with some other function descriptor. The fact that it might not super common for it being used this way doesn't make it less value-based. ------------- PR Comment: https://git.openjdk.org/jdk/pull/30481#issuecomment-4440134705
