Do you see any chance to reproduce the issue? According to https://stackoverflow.com/a/1038504 e.what() can only return nullptr if a custom class returns that (or the iOS stdlib implementation is buggy). If there is an issue we can fix somewhere in the writer implementation, I'd prefer that.

No, unfortunately we don't have a sample or any more info 🤷‍♂️ But we're seeing this crash happening to our users in our crash logging system.

I checked all throw statements and this looks like a bug in the libc++ implementation on iOS. weird.

It is so nice if unrelated compilation issues (see recent wasm build failures) that randomly show up can also randomly disappear again... ;)

Well, in my experience, such random issues unfortunately always come back 😉

(And I was wondering about the wasm build failures already, too).