We got a crash in some code, I had managed to miss this topic entirely somehow. This says:
Pointer authentication can also expose latent bugs in existing code. In C++, it’s incorrect to call a virtual method using a declaration that differs from its definition. In practice, such calls typically succeed in arm64, but trigger a pointer authentication failure in arm64e. You might encounter this bug when using OS_OBJECT types like dispatch_queue_t and xpc_connection_t. You can’t pass instances of these types from C++ code to an Objective-C++ function (or vice versa) because they’re defined differently in Objective-C++ to support automatic reference counting (ARC).
and, yes, we have both C++ and ObjC++ code, and a class does have a dispatch_queue_t member, and it does get passed around (although I don't think anything other than ObjC++ code touches the member), but... the documentation there says "you can't d this" but has absolutely no information on what you are supposed to do instead.
Again, I've managed to miss this completely, and my network searching ability is pretty awful, so I assume I simply couldn't find documentation on it? (And I can't stream video very well where I am right now.)