"Undefined symbols" when trying to Profile in Xcode

[NSExceptional]

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I'm building a Swift Forums client using that JSON library I've been working on the last few months. Wanted to profile it for memory leaks, but the app doesn't link when I try to profile it… It compiles and runs fine outside of that, obviously. What could be causing this?

It's a few runtime functions in CEcho, like _registerTypeMetadata