Crashes related to KVO and UserDefaults about defaults HOT 7 OPEN

Which Defaults version? And which observation methods?

from defaults.

@sindresorhus We are using 7.3 in the latest production, and use the Defaults.publisher(keys:) and Defaults.updates methods.

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All crashes happen on a background queue, which might suggest it is some concurrency issue. UserDefaults is thread safe, but maybe KVO isn't?

The crash happens in Apple's code that notifies about KVO, not the code that subscribes to KVO, so this really seems like UserDefaults itself is accidentally not fully thread-safe.

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Without a way to reproduce the issue locally, I cannot really come up with a workaround. Defaults cannot wrap calls to UserDefaulta in DispatchQueue.main.async as it can cause synchronization issues (for example, if the value is read right after setting it).

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I also have not seen this kind of crash in any of my 40 apps (almost all of them use Defaults).

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You could try this: eef0df0 But it could cause problems if the value is read right after.

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Thanks a lot. I've moved to this branch and will report bck after the next update.

from defaults.