clarkholdham

I've recently encountered the exact same issues as wangjunZeroZeroSeven. I was unable to come up with a perfectly safe solution (outside of removing any spdlog calls from local variable destruction).

@palacaze Wondering if you had any luck testing the edge cases on the branch [perf](https://github.com/palacaze/sigslot/tree/perf). My team and I would greatly benefit from move semantics in this library.