Automatic loading of `PFObject` subclasses does not work on Xcode 16 / iOS 18

New Issue Checklist

[x] I am not disclosing a vulnerability.
[x] I am not just asking a question.
[x] I have searched through existing issues.
[x] I can reproduce the issue with the latest versions of Parse Server and the Parse ObjC SDK.

Issue Description

Parse iOS / OSX SDK uses PFObject instances for basically everything. All subclasses of PFObject are represented in MongoDB/PostgreSQL as collections/tables with given names. Mapping of the PFObject subclasses and their names in MongoDB/PostreSQL need to be known to Parse SDK so that PFObject subclasses can be loaded/stored properly to the database.

Originally registration of all classes was needed to be done manually by invoking code like this after initialising the Parse SDK:

[PFInstallation registerSubclass];
[PFUser registerSublcass];
[PFSession registerSubclass];

Then came https://github.com/parse-community/Parse-SDK-iOS-OSX/pull/967 that made things much simpler by scanning executable bundles (read frameworks) for all classes that are subclassing PFObject and registering them during SDK startup automatically.

The code is here:

https://github.com/parse-community/Parse-SDK-iOS-OSX/blob/c301262e17951e893a76a2448e7ce5f74f49bf85/Parse/Parse/Internal/Object/Subclassing/PFObjectSubclassingController.m#L384-L387

Building with Xcode 16 seems to break the functionality because objc_copyClassNamesForImage returns nothing.

More investigation is needed. I have not yet been able to see if this is a compiler option that needs to be toggled, or some new measure preventing apps from examining available runtime classes and their properties via Objective-C runtime reflection.

Steps to reproduce

Recompile your app with Xcode 16 and try to run against iOS 18. And see if that works for you.

It fails for me with unrelated error:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid class name. Class names cannot start with an underscore.'

This is actually an exception coming from deep inside the Parse SDK where it tries to instantiate PFInstallation with collection name _Installation and failing because PFInstallation class was not registered.

Actual Outcome

Recompiling working code using Xcode 16 breaks the app.

Workaround

For the moment registering all required classes manually seems to work around the problem:

        Parse.initialize(
            with: ParseClientConfiguration() { config in

                config.applicationId = .apiAppIdString
                config.clientKey = .apiKeyString
                config.server = .apiURLString
                config.applicationGroupIdentifier = .appGroup
                config.networkRetryAttempts = 2

        })

        PFInstallation.registerSubclass()
        PFUser.registerSubclass()
        PFSession.registerSubclass()

Environment

Client

Parse ObjC SDK version: master

Server

Parse Server version: master

parse-community / Parse-SDK-iOS-OSX