Possible to fix these issues ?

See my On Log Noise for my general advice here.

The implemented in both message can be a sign of serious problems, but only if one or both of the implementations comes from your code. Here that’s not the case — both implementations come from Apple frameworks — and thus you can ignore the error.

I don’t have any specific input on the errors encountered while discovering extensions message.

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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

I have often seen such messages, and finally just had to ignore them (not very satisfying, but no way to do different).

Maybe we should post bug report (even though, I'm convinced the problem is already known and addressed when possible).

But, as it says: One of the two will be used. Which one is undefined.

So, if both framework are OK (they should, being system framework), they probably behave the same.

Note: however, could this explain, from time to time, that an app behave slightly differently, without any apparent reason ?

however, could this explain, from time to time, that an app behave slightly differently, without any apparent reason ?

No. If both copies of the class come from the OS, they will be built from the same source code and behave identically.

You don’t have to reach for obscure corner cases like this to explain this observation. Any sufficiently large program will contain code that relies on undefined behaviour. This is worse in C-based languages than Swift, but it’s still a factor in Swift. Swift is not entirely free of undefined behaviour itself. Even if it were, the system frameworks that your Swift code relies on are largely written in C-based languages.

Once you admit undefined behaviour into your program, you’re very likely to see some randomness. Some of this is accidental (for example, thread race conditions) and some of it is deliberately introduced for security reasons (for example, ASLR and the randomness in Swift hashing).

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"