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Non-deterministic method selection during reflection

Description

Reflection does not return the same order of methods across JVM invocations (via Class::getMethods). This is probably most apparent when submitting Clojure functions, which are Callable and Runnable, into an executor:

Approach: Sort method options found by the reflector so that the same version is always selected when there is more than one choice.

Patch: CLJ-2413-3.patch

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Alex Miller February 8, 2022 at 7:41 PM

I think this needs to take a few steps back and consider all the places where we get a set of methods (and maybe fields? not sure those will mater) for the purposes of reflection - static methods, instance methods, etc. Maybe if there was a wrapper around the call to reflect stuff everyone could use it.

Ambrose Bonnaire-Sergeant September 20, 2021 at 7:16 PM
Edited

Added patch with tests in CLJ-2413-3.patch. Added myself as coauthor in the patch.

Tested on JVM 8, 11, 16

Ambrose Bonnaire-Sergeant September 20, 2021 at 7:15 PM
Edited

Good to know! Note to self: more on this here.

Ghadi Shayban September 20, 2021 at 7:10 PM

that’s at the language level. At the VM level, methods may have same args, different ret.

Ambrose Bonnaire-Sergeant September 20, 2021 at 7:05 PM

FWIW I don’t think the getReturnType comparison is strictly needed (unless it’s a performance optimization). A method cannot have different return types for the same parameters, so it’s sufficient to just sort by the params.

The compiler does not consider return type when differentiating methods, so you cannot declare two methods with the same signature even if they have a different return type.

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Created October 5, 2018 at 5:09 AM
Updated February 8, 2022 at 7:41 PM